GHSA-P4PM-X7CH-5MVC
Vulnerability from github – Published: 2026-04-24 15:32 – Updated: 2026-04-24 15:32In the Linux kernel, the following vulnerability has been resolved:
rxrpc: Fix RxGK token loading to check bounds
rxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length from the XDR token as u32 values and passes each through round_up(x, 4) before using the rounded value for validation and allocation. When the raw length is >= 0xfffffffd, round_up() wraps to 0, so the bounds check and kzalloc both use 0 while the subsequent memcpy still copies the original ~4 GiB value, producing a heap buffer overflow reachable from an unprivileged add_key() call.
Fix this by:
(1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX.
(2) Sizing the flexible-array allocation from the validated raw key length via struct_size_t() instead of the rounded value.
(3) Caching the raw lengths so that the later field assignments and memcpy calls do not re-read from the token, eliminating a class of TOCTOU re-parse.
The control path (valid token with lengths within bounds) is unaffected.
{
"affected": [],
"aliases": [
"CVE-2026-31641"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-24T15:16:43Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Fix RxGK token loading to check bounds\n\nrxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length\nfrom the XDR token as u32 values and passes each through round_up(x, 4)\nbefore using the rounded value for validation and allocation. When the raw\nlength is \u003e= 0xfffffffd, round_up() wraps to 0, so the bounds check and\nkzalloc both use 0 while the subsequent memcpy still copies the original\n~4 GiB value, producing a heap buffer overflow reachable from an\nunprivileged add_key() call.\n\nFix this by:\n\n (1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket\n lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with\n the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX.\n\n (2) Sizing the flexible-array allocation from the validated raw key\n length via struct_size_t() instead of the rounded value.\n\n (3) Caching the raw lengths so that the later field assignments and\n memcpy calls do not re-read from the token, eliminating a class of\n TOCTOU re-parse.\n\nThe control path (valid token with lengths within bounds) is unaffected.",
"id": "GHSA-p4pm-x7ch-5mvc",
"modified": "2026-04-24T15:32:36Z",
"published": "2026-04-24T15:32:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31641"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3e04596cba8a86cbff9c3f4bf0a524a3a488773c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/49875b360c2b83a3c226e189c502e501d83e6445"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d179a868dd755b0cfcf7582e00943d702b9943b8"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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