138 lines
8.4 KiB
JSON
138 lines
8.4 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-2026-52906",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-06-09T07:44:35.366Z",
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"datePublished": "2026-06-09T12:36:03.521Z",
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"dateUpdated": "2026-08-05T12:31:29.381Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T12:31:29.381Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p: fix access mode flags being ORed instead of replaced\n\nSince commit 1f3e4142c0eb (\"9p: convert to the new mount API\"),\nv9fs_apply_options() applies parsed mount flags with |= onto flags\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\n\"access=user\", both bits end up set. Access mode checks compare\nagainst exact values, so having both bits set matches neither mode.\n\nThis causes v9fs_fid_lookup() to fall through to the default switch\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\nfor all fid lookups. Root is then unable to chown or perform other\nprivileged operations.\n\nFix by clearing the access mask before applying the user's choice."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
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"baseScore": 7.7,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The flaw is reached through local mount and VFS file-operation syscalls (open, read, write, setattr) on a 9p client mount, not through remote packet handling. Even when 9p uses virtio or TCP transport, exploitation requires local access to the mounted filesystem or local CAP_SYS_ADMIN to mount with the triggering options.\nAC:L - An attacker who can mount 9p with 9P2000.L and `access=user` or `access=<uid>` reliably triggers the bug on every fid lookup. On systems where virtio-9p is already mounted with those options, exploitation requires only normal filesystem access with no race or special timing.\nPR:N - Exploitation against an already-mounted vulnerable 9p share requires no elevated privileges—only local shell access to the mount point. The worst case (`access=<uid>` SINGLE mode) is meant to block all other users, yet any unprivileged local user can still obtain fids and access the share.\nUI:N - Once a vulnerable 9p filesystem is mounted, no further victim interaction is required; the attacker simply performs normal file operations. Mounting with the triggering options is attacker-controlled or a one-time administrative setup, not ongoing user interaction at exploitation time.\nS:U - Impact is confined to unauthorized access within the guest/kernel filesystem boundary (bypassing 9p access-mode isolation between local users or against a single-user mount restriction). It does not cross VM-to-host, IOMMU, or sandbox security boundaries beyond the shared 9p export itself.\nC:H - The mangled access mask forces all operations through a shared INVALID_UID attach instead of per-user attaches, breaking confidentiality guarantees of `access=user` and completely defeating `access=<uid>` SINGLE-mode isolation. Unprivileged users can read data on mounts explicitly restricted to another user.\nI:H - The same fid-lookup failure lets unauthorized users perform writes through the shared INVALID_UID attach on mounts where SINGLE or per-user modes should have prevented any access. Server-side authorization keyed to attach identity is undermined, enabling unauthorized modification of files on the export.\nA:N - The bug is a logic error in access-mode handling that misroutes fid lookups; it does not cause kernel oops, panic, hang, or repeatable denial of service. Root losing chown capability on the mount is a localized authorization failure, not system-wide availability loss."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/9p/v9fs.c"
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],
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"versions": [
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{
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"version": "1f3e4142c0eb178089ea0cbc97506a061470ad27",
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"lessThan": "b8f037e87a083291190204b959cda417aaf01058",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "1f3e4142c0eb178089ea0cbc97506a061470ad27",
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"lessThan": "da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9",
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"status": "affected",
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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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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/9p/v9fs.c"
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],
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"versions": [
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{
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"version": "6.19",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.19",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.0.4",
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"lessThanOrEqual": "7.0.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.1",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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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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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.19",
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"versionEndExcluding": "7.0.4"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.19",
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"versionEndExcluding": "7.1"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058"
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},
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{
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"url": "https://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9"
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}
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],
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"title": "9p: fix access mode flags being ORed instead of replaced",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |