CyberSecBulletin
CVE-2026-31696NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-31696 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 44714dfda386884919ba366411880b6fb3c3efd3, 41a117dd80371343babc52198d1114e83eb37627, 9a397aa9b5e53ca63d4d6aefb542832eca389618 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 44714dfda386884919ba366411880b6fb3c3efd3 or 41a117dd80371343babc52198d1114e83eb37627 or 9a397aa9b5e53ca63d4d6aefb542832eca389618 or 1fa36cf495b0023e8475d038535c05e4063211e1, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.136 or 6.12.84 or 6.18.25 or 7.0.2, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, 44714dfda386884919ba366411880b6fb3c3efd3; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, 41a117dd80371343babc52198d1114e83eb37627; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, 9a397aa9b5e53ca63d4d6aefb542832eca389618; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, 1fa36cf495b0023e8475d038535c05e4063211e1; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, 4458757c020592a3094366e0fb20457383b42f92; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, ce383ba615339f8eaec646a166d2c2b015bb5ca0; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, a1be1c9ece26cea69654f28b255ff9a7906b897b; 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 up to, but not including, ac33733b10b484d666f97688561670afd5861383; and 1 more ranges44714dfda386884919ba366411880b6fb3c3efd3, 41a117dd80371343babc52198d1114e83eb37627, 9a397aa9b5e53ca63d4d6aefb542832eca389618, 1fa36cf495b0023e8475d038535c05e4063211e1, 4458757c020592a3094366e0fb20457383b42f92, ce383ba615339f8eaec646a166d2c2b015bb5ca0
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
LinuxLinux Kernel3.17 up to, but not including, 6.6.136; 6.7 up to, but not including, 6.12.84; 6.13 up to, but not including, 6.18.25; 6.19 up to, but not including, 7.0.2; 7.16.6.136, 6.12.84, 6.18.25, 7.0.2

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
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing In rxrpc_preparse(), there are two paths for parsing key payloads: the XDR path (for large payloads) and the non-XDR path (for payloads <= 28 bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR path fails to do so. This allows an unprivileged user to provide a very large ticket length. When this key is later read via rxrpc_read(), the total token size (toksize) calculation results in a value that exceeds AFSTOKEN_LENGTH_MAX, triggering a WARN_ON(). [ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc] Fix this by adding a check in the non-XDR parsing path of rxrpc_preparse() to ensure the ticket length does not exceed AFSTOKEN_RK_TIX_MAX, bringing it into parity with the XDR parsing logic.

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

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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