CyberSecBulletin
CVE-2026-43020NVD status: Analyzed

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-43020 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 0f37d1e65c6d71ad94ccfb5c602163c525db789d, 257cdb960d8ff6d60bb6461b03c814b6cf0c9e64, c34577f517b556fb6ca173d45bf7e766ae2564ce 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 0.13% 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 0f37d1e65c6d71ad94ccfb5c602163c525db789d or 257cdb960d8ff6d60bb6461b03c814b6cf0c9e64 or c34577f517b556fb6ca173d45bf7e766ae2564ce or f71695e81f4cb428f3c7e2138eae88199005b52c, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.168 or 6.6.134, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, 0f37d1e65c6d71ad94ccfb5c602163c525db789d; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, 257cdb960d8ff6d60bb6461b03c814b6cf0c9e64; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, c34577f517b556fb6ca173d45bf7e766ae2564ce; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, f71695e81f4cb428f3c7e2138eae88199005b52c; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, 82f342b3b006ca1d65f4890c05f2ec32fcb808b6; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, 50fb64defa72a3fecd0af1ca7c6b47b5c5c2b257; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, 40ba329e8b4cd2fb11b0caf5e6a543ceaebb6009; 346af67b8d116f01ef696fd47959a55deb2db8b6 up to, but not including, b8dbe9648d69059cfe3a28917bfbf7e61efd7f15; and 1 more ranges0f37d1e65c6d71ad94ccfb5c602163c525db789d, 257cdb960d8ff6d60bb6461b03c814b6cf0c9e64, c34577f517b556fb6ca173d45bf7e766ae2564ce, f71695e81f4cb428f3c7e2138eae88199005b52c, 82f342b3b006ca1d65f4890c05f2ec32fcb808b6, 50fb64defa72a3fecd0af1ca7c6b47b5c5c2b257
LinuxLinux Kernel3.4 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.168; 6.2 up to, but not including, 6.6.134; 6.7 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; 7.05.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22

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: Bluetooth: MGMT: validate LTK enc_size on load Load Long Term Keys stores the user-provided enc_size and later uses it to size fixed-size stack operations when replying to LE LTK requests. An enc_size larger than the 16-byte key buffer can therefore overflow the reply stack buffer. Reject oversized enc_size values while validating the management LTK record so invalid keys never reach the stored key state.

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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