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.
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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 01 Apr 2026 09:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | apparmor: fix differential encoding verification | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-04-01T08:36:38.516Z
Reserved: 2026-01-13T15:37:46.013Z
Link: CVE-2026-23409
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-04-01T09:16:16.913
Modified: 2026-04-01T09:16:16.913
Link: CVE-2026-23409
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.