CVE-2026-31402 (GCVE-0-2026-31402)

Vulnerability from cvelistv5 – Published: 2026-04-03 15:16 – Updated: 2026-04-27 14:02
VLAI?
Title
nfsd: fix heap overflow in NFSv4.0 LOCK replay cache
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request.
Severity ?
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < f9fcb4441f6c02bb20c2eb340101e27dfe23607c (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < c9452c0797c95cf2378170df96cf4f4b3bca7eff (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8afb437ea1f70cacb4bbdf11771fb5c4d720b965 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0f0e2a54a31a7f9ad2915db99156114872317388 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < ae8498337dfdfda71bdd0b807c9a23a126011d76 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5133b61aaf437e5f25b1b396b14242a6bb0508e2 (git)
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    Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.20 , ≤ 6.18.* (semver)
Unaffected: 6.19.10 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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            "fs/nfsd/nfs4xdr.c",
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    "dateUpdated": "2026-04-27T14:02:49.450Z",
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.