CVE-2026-23409

Medium

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix differential encoding verification Differential encoding allows loops to be created if it is abused. To prevent this the unpack should verify that a diff-encode chain terminates. Unfortunately the differential encode verification had two bugs. 1. it conflated states that had gone through check and already been marked, with states that were currently being checked and marked. This means that loops in the current chain being verified are treated as a chain that has already been verified. 2. the order bailout on already checked states compared current chain check iterators j,k instead of using the outer loop iterator i. Meaning a step backwards in states in the current chain verification was being mistaken for moving to an already verified state. Move to a double mark scheme where already verified states get a different mark, than the current chain being kept. This enables us to also drop the backwards verification check that was the cause of the second error as any already verified state is already marked.

Package Linux Kernel
Published 2026-04-01
Last modified 2026-04-24
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-835

CVE-2026-23409 is a Infinite Loop vulnerability

What is Infinite Loop?

The product contains an iteration that does not exit even when it should. Learn more on MITRE CWE

Affected versions

Linux kernel versions 4.17 and later are affected. Fixed in 5.10.253, 5.15.203, 6.1.169, 6.6.130, 6.12.77, 6.18.18, 6.19.8, 7.0 and their respective stable series.

Affected from
≥ 4.17
Fixed in
✓ 5.10.253 5.10.x ✓ 5.15.203 5.15.x ✓ 6.1.169 6.1.x ✓ 6.6.130 6.6.x ✓ 6.12.77 6.12.x ✓ 6.18.18 6.18.x ✓ 6.19.8 6.19.x ✓ 7.0

References

The following references provide additional information about CVE-2026-23409 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

8 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2026-23409?

    CVE-2026-23409 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as an Infinite Loop flaw (CWE-835) . It affects Linux kernel versions from 4.17 onward and has been patched in 5.10.253, 5.15.203, 6.1.169 and others. CVE-2026-23409 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-23409?

    CVE-2026-23409 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2026-23409?

    Yes — CVE-2026-23409 has been patched. Fixed versions include 5.10.253, 5.15.203, 6.1.169 and others. If you are running Linux kernel 4.17 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-23409 actively exploited?

    No — CVE-2026-23409 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Infinite Loop (CWE-835)?

    The product contains an iteration that does not exit even when it should. View CWE-835 on MITRE CWE →

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