CyberSecBulletin
CVE-2026-43490NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-43490 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 00f053d97b63591cafd791dce8d6c53e1625dad1, a7fb771314fb3a265d30f8ac245869a367ab065c, 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 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 0.43% 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 00f053d97b63591cafd791dce8d6c53e1625dad1 or a7fb771314fb3a265d30f8ac245869a367ab065c or 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 or 1aa60fea7f637c071f529ad6784aecca2f2f0c5f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.141 or 6.12.88 or 6.18.30 or 7.0.7, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxe2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 00f053d97b63591cafd791dce8d6c53e1625dad1; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, a7fb771314fb3a265d30f8ac245869a367ab065c; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 47c6e37a77b10e74f70d845ba4ea5d3cafa00336; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 1aa60fea7f637c071f529ad6784aecca2f2f0c5f; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, c1d95c995d5bcb24b639200a899eda59cb1e6d64; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 996454bc0da84d5a1dedb1a7861823087e01a7ae; 5.1500f053d97b63591cafd791dce8d6c53e1625dad1, a7fb771314fb3a265d30f8ac245869a367ab065c, 47c6e37a77b10e74f70d845ba4ea5d3cafa00336, 1aa60fea7f637c071f529ad6784aecca2f2f0c5f, c1d95c995d5bcb24b639200a899eda59cb1e6d64, 996454bc0da84d5a1dedb1a7861823087e01a7ae
LinuxLinux Kernel5.15 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.88; 6.13 up to, but not including, 6.18.30; 6.19 up to, but not including, 7.0.7; 7.16.6.141, 6.12.88, 6.18.30, 7.0.7

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: validate inherited ACE SID length smb_inherit_dacl() walks the parent directory DACL loaded from the security descriptor xattr. It verifies that each ACE contains the fixed SID header before using it, but does not verify that the variable-length SID described by sid.num_subauth is fully contained in the ACE. A malformed inheritable ACE can advertise more subauthorities than are present in the ACE. compare_sids() may then read past the ACE. smb_set_ace() also clamps the copied destination SID, but used the unchecked source SID count to compute the inherited ACE size. That could advance the temporary inherited ACE buffer pointer and nt_size accounting past the allocated buffer. Fix this by validating the parent ACE SID count and SID length before using the SID during inheritance. Compute the inherited ACE size from the copied SID so the size matches the bounded destination SID. Reject the inherited DACL if size accumulation would overflow smb_acl.size or the security descriptor allocation size.

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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