apparmor: fix differential encoding verification
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-835.
Summary
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.17 and later | 5.10.253, 5.15.203, 6.1.169, 6.6.130, 6.12.77, 6.18.18, 6.19.8, 7.0 | Patch available | CNA |
- Linux VendorLinux Affected 4.17 and later 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 Patch available CNA
CPE configurations NVD · 9
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 4.17.1 to before 5.10.253; 5.11 to before 5.15.203; 5.16 to before 6.1.169; 6.2 to before 6.6.130; 6.7 to before 6.12.77; 6.13 to before 6.18.18; 6.19 to before 6.19.8 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:4.17:-:*:*:*:*:*:* | 4.17 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* | 7.0 rc1 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* | 7.0 rc2 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* | 7.0 rc3 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* | 7.0 rc4 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* | 7.0 rc5 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* | 7.0 rc6 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* | 7.0 rc7 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.17.1 to before 5.10.253; 5.11 to before 5.15.203; 5.16 to before 6.1.169; 6.2 to before 6.6.130; 6.7 to before 6.12.77; 6.13 to before 6.18.18; 6.19 to before 6.19.8 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:4.17:-:*:*:*:*:*:* Versions 4.17 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* Versions 7.0 rc1 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* Versions 7.0 rc2 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* Versions 7.0 rc3 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* Versions 7.0 rc4 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* Versions 7.0 rc5 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* Versions 7.0 rc6 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* Versions 7.0 rc7 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) 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
Vendor assessments
Red Hat
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2026-23409
- 2026-10-03 Alias added: GHSA-53jf-v56h-xgqg
References
Patch 8
- https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84
- https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a
- https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0
- https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a
- https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167
- https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a
- https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa
- https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093
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- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2026-23409 · CVE Program
- CVE-2026-23409 · NVD
- FIRST EPSS
- GHSA-53jf-v56h-xgqg · GitHub Advisory Database · CC BY 4.0
- CVE-2026-23409 · Red Hat security data · CC BY 4.0
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