Linux: Out-of-bounds Write

What to do

1. Update Linux to f9fcb4441f6c02bb20c2eb340101e27dfe23607c or 2665887a69437a8a4f552f69509eecfb73d4aa19 or c9452c0797c95cf2378170df96cf4f4b3bca7eff or 8afb437ea1f70cacb4bbdf11771fb5c4d720b965, whichever matches your release line, or a later version.
2. Update Linux Kernel to 5.10.253 or 6.1.167 or 6.6.130 or 6.12.78, whichever matches your release line, or a later version.
3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector

NetworkCan be exploited remotely over a network, including the internet.

Attack complexity

LowNo special conditions are needed; the attack works reliably.

Privileges required

NoneNo account or login is needed.

User interaction

NoneNo action by a victim is required.

Scope

UnchangedImpact stays within the vulnerable component.

Confidentiality

HighAll data handled by the component can be read.

Integrity

HighData or code can be modified at will.

Availability

HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

Timeline

1. April 3, 2026CVE record published.
2. October 16, 2026CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
3. November 10, 2026Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-31401Apr 3, 2026Linux
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-23422Apr 3, 2026Linux
• 8.8 High severity

  macOS: Out-of-bounds Write

  CVE-2025-43219Apr 2, 2026Apple
• 8.8 High severity

  iOS and iPadOS: Out-of-bounds Write

  CVE-2025-43202Apr 2, 2026Apple
• 8.8 High severity

  DNS-120: Out-of-bounds Write

  CVE-2026-5214Mar 31, 2026D-Link
• 8.8 High severity

  DNS-120: Out-of-bounds Write

  CVE-2026-5213Mar 31, 2026D-Link

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