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vuln-cve/data/2026/12xxx/CVE-2026-12633.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-12633",
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"state": "PUBLISHED",
"assignerShortName": "zephyr",
"dateReserved": "2026-06-18T15:22:29.825Z",
"datePublished": "2026-08-19T20:37:34.532Z",
"dateUpdated": "2026-11-04T04:59:33.616Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr",
"dateUpdated": "2026-11-04T04:59:33.616Z"
},
"title": "Out-of-bounds write in IPv6 6LoWPAN Context Option handling via unauthenticated Router Advertisement",
"descriptions": [
{
"lang": "en",
"value": "The IPv6 neighbor-discovery code in subsys/net/ip/ipv6_nbr.c processes the 6LoWPAN Context Option (6CO, RFC 6775) carried inside ICMPv6 Router Advertisements. In handle_ra_6co() the 8-bit context_len field is taken directly from the packet and was never bounded to the RFC maximum of 128. The function computes context->context_len / 8 and then performs memset(context->prefix + context_len, 0, sizeof(context->prefix) - context_len), where context->prefix is a fixed 16-byte array.\n\nWith context_len between 136 and 255 (and the option length field set to 3, which the pre-fix validation accepts), context_len / 8 evaluates to 17..31, so the memset length 16 - context_len/8 underflows the unsigned size_t argument to roughly SIZE_MAX. This produces an unbounded out-of-bounds memset that zeroes kernel memory well past the 6lo context structure.\n\nThe defect is reachable from unauthenticated, link-local input: any host on the same link can send a crafted Router Advertisement with a 6CO option. The RA handler validates only the option length field before calling handle_ra_6co(), so a single packet triggers the wild write. The code is compiled when CONFIG_NET_6LO_CONTEXT is enabled.\n\nThe impact is a reliable remote (adjacent) denial of service via memory corruption, with collateral integrity loss as the memset zeroes contiguous memory before the system faults. Router Advertisements are link-scoped and not forwarded, so the attacker must be on the same link (AV:A). The fix rejects any context_len greater than 128 before the length computation."
}
],
"affected": [
{
"vendor": "zephyrproject",
"product": "zephyr",
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"packageName": "zephyr",
"defaultStatus": "unaffected",
"programFiles": [
"subsys/net/ip/ipv6_nbr.c"
],
"versions": [
{
"version": "1.8.0",
"status": "affected",
"versionType": "semver",
"lessThan": "4.3.2"
},
{
"version": "4.4.0",
"status": "affected",
"versionType": "semver",
"lessThan": "4.4.2"
}
]
}
],
"references": [
{
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b",
"name": "Fix commit",
"tags": [
"patch"
]
},
{
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-h5m5-hm6j-cgpf",
"name": "GHSA-h5m5-hm6j-cgpf"
}
],
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{
"format": "CVSS",
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
"baseScore": 8.1,
"baseSeverity": "HIGH"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"description": "memory-safety",
"cweId": "CWE-787",
"type": "CWE"
}
]
}
],
"x_generator": {
"engine": "cvelib 1.8.0"
}
},
"adp": [
{
"metrics": [
{
"other": {
"type": "ssvc",
"content": {
"id": "CVE-2026-12633",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-08-20T15:16:15.491668Z"
}
}
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP",
"dateUpdated": "2026-08-20T15:26:33.782Z"
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}