Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: apparmor: fix differential encoding verification Differential encoding allows… (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. 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.
Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: apparmor: fix differential encoding verification Differential encoding allows… (CVE-2026-23409)
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 v3.1
Score 5.5medium
Affected software
pkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=xenialpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/[email protected]~18.04.2?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email 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protected]?arch=source&distro=bluefield/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-23409
- Osv Schema Version
- 1.7.0
- Aliases
- []
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:FIPS-updates:20.04:LTS","Ubuntu:Pro:FIPS:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Nvidia-BlueField:22.04:LTS","Ubuntu:Pro:FIPS-preview:22.04:LTS","Ubuntu:Pro:FIPS-updates:22.04:LTS","Ubuntu:Pro:Realtime:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Nvidia-BlueField:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:Pro:Realtime:24.04:LTS","Ubuntu:25.10"]
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a5b628e2d1edb114c88eea8
Added to database: 07/18/2026, 11:25:02 UTC
Last updated: 07/31/2026, 19:30:34 UTC
Views: 3
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