FKIE_CVE-2026-31641

Vulnerability from fkie_nvd - Published: 2026-04-24 15:16 - Updated: 2026-04-24 17:51
Severity ?
Summary
In 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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3e04596cba8a86cbff9c3f4bf0a524a3a488773c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/49875b360c2b83a3c226e189c502e501d83e6445
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d179a868dd755b0cfcf7582e00943d702b9943b8
Impacted products
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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": "CVE-2026-31641",
  "lastModified": "2026-04-24T17:51:40.810",
  "metrics": {},
  "published": "2026-04-24T15:16:43.463",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3e04596cba8a86cbff9c3f4bf0a524a3a488773c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/49875b360c2b83a3c226e189c502e501d83e6445"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d179a868dd755b0cfcf7582e00943d702b9943b8"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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