CVE-2026-23409apparmor: fix differential encoding verification
- 5.5MediumCVSS base score
- 0.18%Exploitation in 30 daysEPSS · top 92% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By Linux
- 3 months later
· 3 months later
Published
- 40 days later
· 40 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Analyzed | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.18% · top 92% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 1439150cd3c411228b387ab5efca92199d2a659a
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 0fab44285445e9012674396d5c1236a67da518e0
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 34fc60b125ed1d4eb002c76b0664bf0619492167
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 623a9d211bbbb031bb1cbdb38b23487648167f8a
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 1ff4857fac56ac5a90ee63b24db05fa5e91a45aa
- affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 – < 39440b137546a3aa383cfdabc605fb73811b6093
- affected 4.17
- unaffected < 4.17
- unaffected 5.10.253 – ≤ 5.10.*
- unaffected 5.15.203 – ≤ 5.15.*
- unaffected 6.1.169 – ≤ 6.1.*
- unaffected 6.6.130 – ≤ 6.6.*
- unaffected 6.12.77 – ≤ 6.12.*
- unaffected 6.18.18 – ≤ 6.18.*
- unaffected 6.19.8 – ≤ 6.19.*
- unaffected 7.0 – ≤ *
References
References8
- https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84 (opens in a new tab)
- https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a (opens in a new tab)
- https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0 (opens in a new tab)
- https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a (opens in a new tab)
- https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167 (opens in a new tab)
- https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a (opens in a new tab)
- https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa (opens in a new tab)
- https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-17839 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-23409)Record last updated .