CyberSecBulletin
CVE-2026-31432NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-31432 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 533f84264e28c54a79257ea87d2f94a0fcc9a611, 850452af77f55d185f9445e1f7a1db53c5e4aad4, d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09 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 0.55% 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 533f84264e28c54a79257ea87d2f94a0fcc9a611 or 850452af77f55d185f9445e1f7a1db53c5e4aad4 or d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09 or 075ea208c648cc2bcd616295b711d3637c61de45, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.16 or 6.2 or 6.12.81 or 6.18.22, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux9f297df20d93411c0b4ddad7f88ba04a7cd36e77 up to, but not including, 533f84264e28c54a79257ea87d2f94a0fcc9a611; e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d up to, but not including, 850452af77f55d185f9445e1f7a1db53c5e4aad4; e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d up to, but not including, d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09; e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d up to, but not including, 075ea208c648cc2bcd616295b711d3637c61de45; e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d up to, but not including, 515c2daab46021221bdf406bef19bc90a44ec617; e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d up to, but not including, fda9522ed6afaec45cabc198d8492270c394c7bc; f2283680a80571ca82d710bc6ecd8f8beac67d63; 6.1.71 up to, but not including, 6.1.191; and 2 more ranges533f84264e28c54a79257ea87d2f94a0fcc9a611, 850452af77f55d185f9445e1f7a1db53c5e4aad4, d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09, 075ea208c648cc2bcd616295b711d3637c61de45, 515c2daab46021221bdf406bef19bc90a44ec617, fda9522ed6afaec45cabc198d8492270c394c7bc
LinuxLinux Kernel5.15.145 up to, but not including, 5.16; 6.1.71 up to, but not including, 6.2; 6.6 up to, but not including, 6.12.81; 6.13 up to, but not including, 6.18.22; 6.19 up to, but not including, 6.19.12; 7.05.16, 6.2, 6.12.81, 6.18.22, 6.19.12

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
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:N/AC:L/PR:L/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: ksmbd: fix OOB write in QUERY_INFO for compound requests When a compound request such as READ + QUERY_INFO(Security) is received, and the first command (READ) consumes most of the response buffer, ksmbd could write beyond the allocated buffer while building a security descriptor. The root cause was that smb2_get_info_sec() checked buffer space using ppntsd_size from xattr, while build_sec_desc() often synthesized a significantly larger descriptor from POSIX ACLs. This patch introduces smb_acl_sec_desc_scratch_len() to accurately compute the final descriptor size beforehand, performs proper buffer checking with smb2_calc_max_out_buf_len(), and uses exact-sized allocation + iov pinning.

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. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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