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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-31402

nfsd: fix heap overflow in NFSv4.0 LOCK replay cache

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < f9fcb4441f6c02bb20c2eb340101e27dfe23607caffected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 2665887a69437a8a4f552f69509eecfb73d4aa19affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < c9452c0797c95cf2378170df96cf4f4b3bca7effaffected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 8afb437ea1f70cacb4bbdf11771fb5c4d720b965affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 0f0e2a54a31a7f9ad2915db99156114872317388affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < ae8498337dfdfda71bdd0b807c9a23a126011d76affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 5133b61aaf437e5f25b1b396b14242a6bb0508e2affected

Linux Linux

Default version status: affected

  • 2.6.12affected
  • 0 to < 2.6.12unaffected
  • 5.10.253 to ≤ 5.10.*unaffected
  • 5.15.210 to ≤ 5.15.*unaffected
  • 6.1.167 to ≤ 6.1.*unaffected
  • 6.6.130 to ≤ 6.6.*unaffected
  • 6.12.78 to ≤ 6.12.*unaffected
  • 6.18.20 to ≤ 6.18.*unaffected
  • 6.19.10 to ≤ 6.19.*unaffected
  • 7.0 to ≤ *unaffected

References