CVE-2026-23409
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.
Does this matter?
Lower severity and a low EPSS score (0.18%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.18% probability · 7th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-835
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0Patch
- https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659aPatch
- https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aaPatch
- https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167Patch
- https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093Patch
- https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8aPatch
- https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4aPatch
- https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.