CVE-2026-23409
What it is
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.
At a glance
- Exploitability
- Can be exploited locally on the machine with a low-privilege account. High risk of service disruption.
- Exploit odds
- 0.2% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.2% in the next 30 days (EPSS).
- Severity: 5.5 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.2% · EPSS, next 30 days
- Weakness
- CWE-835
- Record status
- Analyzed
Affected
- Linux Kernel < 5.10.253
- Linux Kernel < 5.15.203
- Linux Kernel < 6.1.169
- Linux Kernel < 6.6.130
- Linux Kernel < 6.12.77
- Linux Kernel < 6.18.18
- Linux Kernel < 6.19.8
- Linux Kernel 4.17
Attack profile CVSS 3.1 · 5.5
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-23409.md and follow it. Check whether this project is affected by CVE-2026-23409. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0
- https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a
- https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa
- https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167
- https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093
- https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a
- https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a
- https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84
References
- https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0
- https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a
- https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa
- https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167
- https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093
- https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a
- https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a
- https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84