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CVE-2026-90231 — Linux kernel

CVE-2026-90231 is a security vulnerability. No vendor fix is recorded yet; mitigation options are listed below.

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix unconfined user namespace restriction forced stack If a task is already confined by a stack the unprivileged…

Published
Sep 17, 2026
Updated
Sep 17, 2026
Affected
—
Patched
—
Exploits
None indexed
Exploitation data as of Sep 18, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

In the Linux kernel, the following vulnerability has been resolved:

apparmor: fix unconfined user namespace restriction forced stack

If a task is already confined by a stack the unprivileged transition restriction on unconfined is not correctly, applied. This results in an escape if two transitions through an unconfined profile can be executed.

Fix this by pushing the check into the per profile label build. The check will always be done against unconfined and result in a stack of just the unconfined component when necessary.

Detection & mitigation playbook

Vulnerability

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    No patched version of the affected component has shipped for CVE-2026-90231 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-90231 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-90231. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix unconfined user namespace restriction forced stack If a task is already confined by a stack the unprivileged transition restriction on unconfined is not correctly, applied. This results in an escape if two transitions through an unconfined profile can be executed. Fix this by pushing the check into the per profile label build. The check will always be done against unconfined and result in a stack of just the unconfined component when necessary.
O3 Security · Impact-Aware SCA

Is CVE-2026-90231 in your dependencies?

O3 Security finds CVE-2026-90231 across dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works