346 lines
20 KiB
JSON
346 lines
20 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-91187",
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"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
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"state": "PUBLISHED",
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"assignerShortName": "EEF",
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"dateReserved": "2026-09-15T15:30:01.892Z",
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"datePublished": "2026-09-24T13:20:52.974Z",
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"dateUpdated": "2026-09-24T14:47:30.520Z"
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},
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"containers": {
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"cna": {
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"affected": [
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{
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"collectionURL": "https://repo.hex.pm",
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"cpes": [
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"cpe:2.3:a:dashbit:nimble_zta:*:*:*:*:*:*:*:*"
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],
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"defaultStatus": "unaffected",
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"modules": [
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"'Elixir.NimbleZTA.Cloudflare'"
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],
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"packageName": "nimble_zta",
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"packageURL": "pkg:hex/nimble_zta",
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"product": "nimble_zta",
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"programFiles": [
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"lib/nimble_zta/cloudflare.ex"
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],
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"programRoutines": [
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{
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"name": "'Elixir.NimbleZTA.Cloudflare':authenticate/3"
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},
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{
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"name": "'Elixir.NimbleZTA.Cloudflare':verify_token/2"
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}
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],
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"repo": "https://github.com/dashbitco/nimble_zta",
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"vendor": "dashbit",
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"versions": [
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{
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"lessThan": "0.1.3",
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"status": "affected",
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"version": "0.1.2",
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"versionType": "semver"
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}
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]
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},
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{
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"collectionURL": "https://github.com",
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"cpes": [
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"cpe:2.3:a:dashbit:nimble_zta:*:*:*:*:*:*:*:*"
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],
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"defaultStatus": "unaffected",
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"modules": [
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"'Elixir.NimbleZTA.Cloudflare'"
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],
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"packageName": "dashbitco/nimble_zta",
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"packageURL": "pkg:github/dashbitco/nimble_zta",
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"product": "nimble_zta",
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"programFiles": [
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"lib/nimble_zta/cloudflare.ex"
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],
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"programRoutines": [
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{
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"name": "'Elixir.NimbleZTA.Cloudflare':authenticate/3"
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},
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{
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"name": "'Elixir.NimbleZTA.Cloudflare':verify_token/2"
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}
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],
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"repo": "https://github.com/dashbitco/nimble_zta",
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"vendor": "dashbit",
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"versions": [
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{
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"lessThan": "6458fd18a5ba41166d4973214c519e98fe05b72d",
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"status": "affected",
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"version": "bc004b70985ae5763901baab3a4e204047899768",
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"versionType": "git"
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}
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]
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}
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],
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"configurations": [
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{
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"lang": "en",
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"supportingMedia": [
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{
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"base64": false,
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"type": "text/html",
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"value": "<p>The application must add <code>NimbleZTA.Cloudflare</code> to its supervision tree and authenticate requests through it.</p>"
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},
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{
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"base64": false,
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"type": "text/markdown",
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"value": "The application must add `NimbleZTA.Cloudflare` to its supervision tree and authenticate requests through it."
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}
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],
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"value": "The application must add NimbleZTA.Cloudflare to its supervision tree and authenticate requests through it."
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"cpeMatch": [
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{
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"criteria": "cpe:2.3:a:dashbit:nimble_zta:*:*:*:*:*:*:*:*",
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"versionEndExcluding": "0.1.3",
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"versionStartIncluding": "0.1.2",
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"vulnerable": true
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}
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],
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"negate": false,
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"operator": "OR"
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}
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],
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"operator": "AND"
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}
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],
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"credits": [
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{
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"lang": "en",
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"type": "finder",
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"value": "Kazlu"
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},
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{
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"lang": "en",
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"type": "remediation developer",
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"value": "José Valim / Dashbit"
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},
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{
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"lang": "en",
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"type": "coordinator",
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"value": "Jonatan Männchen / EEF"
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}
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],
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"dateAssigned": "2026-09-24T09:09:36.000Z",
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"descriptions": [
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{
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"lang": "en",
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"supportingMedia": [
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{
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"base64": false,
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"type": "text/html",
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"value": "<p>Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected.</p>\n<p><code>verify_token/2</code> in <code>lib/nimble_zta/cloudflare.ex</code> matches the result of <code>JOSE.JWT.verify/2</code> against <code>{_, token, _s}</code>, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the <code>cf-access-jwt-assertion</code> header, carrying the expected <code>iss</code> claim and the seven service token claims. <code>verify_iss/2</code> reads the <code>iss</code> claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity.</p>\n<p>This issue affects nimble_zta: from 0.1.2 before 0.1.3.</p>"
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},
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{
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"base64": false,
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"type": "text/markdown",
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"value": "Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected.\n\n`verify_token/2` in `lib/nimble_zta/cloudflare.ex` matches the result of `JOSE.JWT.verify/2` against `{_, token, _s}`, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the `cf-access-jwt-assertion` header, carrying the expected `iss` claim and the seven service token claims. `verify_iss/2` reads the `iss` claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity.\n\nThis issue affects nimble_zta: from 0.1.2 before 0.1.3."
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}
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],
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"value": "Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected.\n\nverify_token/2 in lib/nimble_zta/cloudflare.ex matches the result of JOSE.JWT.verify/2 against {_, token, _s}, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the cf-access-jwt-assertion header, carrying the expected iss claim and the seven service token claims. verify_iss/2 reads the iss claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity.\n\nThis issue affects nimble_zta: from 0.1.2 before 0.1.3."
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}
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],
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"impacts": [
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{
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"capecId": "CAPEC-475",
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"descriptions": [
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{
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"lang": "en",
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"supportingMedia": [
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{
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"base64": false,
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"type": "text/html",
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"value": "<p>The attacker authenticates as an arbitrary Cloudflare service token without holding the Cloudflare signing key. The application receives the <code>client_id</code> and the claims of the forged token as the authenticated identity, so the attacker gets the access that the application grants to that service token.</p>"
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},
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{
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"base64": false,
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"type": "text/markdown",
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"value": "The attacker authenticates as an arbitrary Cloudflare service token without holding the Cloudflare signing key. The application receives the `client_id` and the claims of the forged token as the authenticated identity, so the attacker gets the access that the application grants to that service token."
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}
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],
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"value": "The attacker authenticates as an arbitrary Cloudflare service token without holding the Cloudflare signing key. The application receives the client_id and the claims of the forged token as the authenticated identity, so the attacker gets the access that the application grants to that service token."
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}
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]
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}
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],
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"metrics": [
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{
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"cvssV4_0": {
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"Automatable": "NOT_DEFINED",
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"Recovery": "NOT_DEFINED",
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"Safety": "NOT_DEFINED",
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"attackComplexity": "LOW",
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"attackRequirements": "NONE",
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"attackVector": "NETWORK",
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"baseScore": 9.3,
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"baseSeverity": "CRITICAL",
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"privilegesRequired": "NONE",
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"providerUrgency": "NOT_DEFINED",
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"subAvailabilityImpact": "NONE",
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"subConfidentialityImpact": "HIGH",
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"subIntegrityImpact": "HIGH",
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"userInteraction": "NONE",
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"valueDensity": "NOT_DEFINED",
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"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N",
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"version": "4.0",
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"vulnAvailabilityImpact": "NONE",
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"vulnConfidentialityImpact": "HIGH",
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"vulnIntegrityImpact": "NONE",
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"vulnerabilityResponseEffort": "NOT_DEFINED"
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},
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"format": "CVSS",
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"scenarios": [
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{
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"lang": "en",
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"value": "GENERAL"
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}
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]
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}
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],
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"problemTypes": [
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{
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"descriptions": [
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{
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"cweId": "CWE-347",
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"description": "CWE-347 Improper Verification of Cryptographic Signature",
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"lang": "en",
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"type": "CWE"
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}
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]
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}
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],
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"providerMetadata": {
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"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
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"shortName": "EEF",
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"dateUpdated": "2026-09-24T13:20:52.974Z"
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},
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"references": [
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{
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"name": "GitHub Advisory",
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"tags": [
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"related",
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"vendor-advisory"
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],
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"url": "https://github.com/dashbitco/nimble_zta/security/advisories/GHSA-rj24-g8cc-g7g2"
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},
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{
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"name": "EEF CNA record for CVE-2026-91187",
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"tags": [
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"related"
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],
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"url": "https://cna.erlef.org/cves/CVE-2026-91187.html"
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},
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{
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"name": "OSV record EEF-CVE-2026-91187",
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"tags": [
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"related"
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],
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"url": "https://osv.dev/vulnerability/EEF-CVE-2026-91187"
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},
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{
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"name": "Introducing commit bc004b7 in dashbitco/nimble_zta",
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"tags": [
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"related"
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],
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"url": "https://github.com/dashbitco/nimble_zta/commit/bc004b70985ae5763901baab3a4e204047899768"
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},
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{
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"name": "Fix commit 6458fd1 in dashbitco/nimble_zta",
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"tags": [
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"patch"
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],
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"url": "https://github.com/dashbitco/nimble_zta/commit/6458fd18a5ba41166d4973214c519e98fe05b72d"
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}
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],
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"source": {
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"discovery": "EXTERNAL"
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},
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"title": "Improper Verification of Cryptographic Signature in dashbit nimble_zta Cloudflare strategy",
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"workarounds": [
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{
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"lang": "en",
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"supportingMedia": [
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{
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"base64": false,
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"type": "text/html",
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"value": "<p>Disable the Cloudflare authentication strategy.</p>\n<p>To keep the user identity strategy available, reject the service token requests yourself. Examine each request before you call <code>NimbleZTA.Cloudflare.authenticate/3</code>, and reject it if its JWT carries the <code>common_name</code> claim and the <code>type</code> claim.</p>"
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},
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{
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"base64": false,
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"type": "text/markdown",
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"value": "Disable the Cloudflare authentication strategy.\n\nTo keep the user identity strategy available, reject the service token requests yourself. Examine each request before you call `NimbleZTA.Cloudflare.authenticate/3`, and reject it if its JWT carries the `common_name` claim and the `type` claim."
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}
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],
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"value": "Disable the Cloudflare authentication strategy.\n\nTo keep the user identity strategy available, reject the service token requests yourself. Examine each request before you call NimbleZTA.Cloudflare.authenticate/3, and reject it if its JWT carries the common_name claim and the type claim."
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}
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],
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"x_proofOfConcept": [
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{
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"lang": "en",
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"supportingMedia": [
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{
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"base64": false,
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"type": "text/html",
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"value": "<ol>\n<li>Build a JWT payload that carries the <code>aud</code>, <code>common_name</code>, <code>exp</code>, <code>iat</code>, <code>iss</code>, <code>sub</code> and <code>type</code> claims. Use the <code>iss</code> the application expects, set <code>exp</code> to a future timestamp, and set <code>common_name</code> to the service token to impersonate.</li>\n<li>Append any signature segment. The segment must be present, because <code>JOSE.JWT.verify/2</code> needs three segments to parse the token. The signature does not need to verify against the Cloudflare keys.</li>\n<li>Send a request to the application with the forged JWT in the <code>cf-access-jwt-assertion</code> header.</li>\n<li><code>NimbleZTA.Cloudflare.authenticate/3</code> returns the claims of the forged token as the authenticated identity, with the <code>strategy</code> field set to <code>service_token</code>.</li>\n</ol>"
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},
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{
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"base64": false,
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"type": "text/markdown",
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"value": "1. Build a JWT payload that carries the `aud`, `common_name`, `exp`, `iat`, `iss`, `sub` and `type` claims. Use the `iss` the application expects, set `exp` to a future timestamp, and set `common_name` to the service token to impersonate.\n2. Append any signature segment. The segment must be present, because `JOSE.JWT.verify/2` needs three segments to parse the token. The signature does not need to verify against the Cloudflare keys.\n3. Send a request to the application with the forged JWT in the `cf-access-jwt-assertion` header.\n4. `NimbleZTA.Cloudflare.authenticate/3` returns the claims of the forged token as the authenticated identity, with the `strategy` field set to `service_token`."
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}
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],
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"value": "* Build a JWT payload that carries the aud, common_name, exp, iat, iss, sub and type claims. Use the iss the application expects, set exp to a future timestamp, and set common_name to the service token to impersonate.\n* Append any signature segment. The segment must be present, because JOSE.JWT.verify/2 needs three segments to parse the token. The signature does not need to verify against the Cloudflare keys.\n* Send a request to the application with the forged JWT in the cf-access-jwt-assertion header.\n* NimbleZTA.Cloudflare.authenticate/3 returns the claims of the forged token as the authenticated identity, with the strategy field set to service_token."
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}
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]
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},
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"adp": [
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{
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"metrics": [
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{
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"other": {
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"type": "ssvc",
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"content": {
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"timestamp": "2026-09-24T14:43:06.738544Z",
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"id": "CVE-2026-91187",
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"options": [
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{
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"Exploitation": "none"
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},
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{
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"Automatable": "yes"
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},
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{
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"Technical Impact": "partial"
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}
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],
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"role": "CISA Coordinator",
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"version": "2.0.3"
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}
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}
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2026-09-24T14:47:30.520Z"
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}
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}
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]
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}
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} |