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VulnerabilityPublished Updated

CVE-2026-31402: Linux kernel · Out-of-bounds Write

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in f9fcb4441f6c02bb20c2eb340101e27dfe23607c : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
1.1% chance of exploitation in 30 days – higher than 67% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in f9fcb4441f6c02bb20c2eb340101e27dfe23607c, dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0, c9452c0797c95cf2378170df96cf4f4b3bca7eff +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < f9fcb4441f6c02bb20c2eb340101e27dfe23607c
Fixed in
  • f9fcb4441f6c02bb20c2eb340101e27dfe23607c
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0
Fixed in
  • dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < c9452c0797c95cf2378170df96cf4f4b3bca7eff
Fixed in
  • c9452c0797c95cf2378170df96cf4f4b3bca7eff
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ae8498337dfdfda71bdd0b807c9a23a126011d76
Fixed in
  • ae8498337dfdfda71bdd0b807c9a23a126011d76
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 2665887a69437a8a4f552f69509eecfb73d4aa19
Fixed in
  • 2665887a69437a8a4f552f69509eecfb73d4aa19
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 5133b61aaf437e5f25b1b396b14242a6bb0508e2
Fixed in
  • 5133b61aaf437e5f25b1b396b14242a6bb0508e2

AI-suggested

A fix for this vulnerability is available and has been applied in multiple Linux kernel commits. The fix adds bounds checking to prevent copying oversized LOCK denied responses into the replay cache buffer. Users should update their Linux kernel to a fixed version containing these commits. No other mitigations or workarounds are noted in the vendor advisory.

Description

A heap overflow vulnerability exists in the Linux kernel's NFSv4.0 server (nfsd) due to an undersized replay cache buffer that does not account for large lock owner strings in LOCK denied responses. This flaw can be triggered remotely by an unauthenticated attacker using two cooperating NFSv4.0 clients, leading to a slab-out-of-bounds write that corrupts adjacent heap memory. The issue has been fixed by adding a length check before copying responses into the replay buffer, skipping caching if the response is too large while still caching the status. The vulnerability has a critical severity with a CVSS score of 9.8 and affects Linux kernel version 2.6.12. No known exploits in the wild have been reported.

References

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