Linux KernelOperating system · Linux
CVE-2026-23409
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisCrafted input drives a loop whose exit condition is never satisfied, hanging the thread and starving the service of the resource it occupies. A single request can be enough to take a worker down. Remediation is bounding iteration counts and validating the conditions that are supposed to terminate the loop.
General guidance for the infinite loop class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 4.17.1, < 5.10.253>= 5.11, < 5.15.203>= 5.16, < 6.1.169>= 6.2, < 6.6.130>= 6.7, < 6.12.77>= 6.13, < 6.18.18>= 6.19, < 6.19.8= 4.17= 7.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.10.2535.15.2036.1.169
Upgrade to kernel 5.10.253+, 5.15.203+, 6.1.169+, or 6.6.130+ (depending on which major branch is in use)
- Identify the current kernel version using 'uname -r' or 'cat /proc/version'
- Determine which major kernel branch is in use (e.g., 5.10.x, 5.15.x, 6.1.x, or 6.2.x)
- For systems on kernel 4.17.1 to 5.10.x: upgrade to kernel version 5.10.253 or later
- For systems on kernel 5.11 to 5.15.x: upgrade to kernel version 5.15.203 or later
- For systems on kernel 5.16 to 6.1.x: upgrade to kernel version 6.1.169 or later
- For systems on kernel 6.2 to 6.6.x: upgrade to kernel version 6.6.130 or later
- Apply the kernel update via distribution package manager (e.g., apt-get update && apt-get upgrade, yum update, or dnf update)
- Reboot the system to load the fixed kernel
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-23409 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-23409 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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