# CVE-2010-4344: Exim Heap-Based Buffer Overflow Vulnerability

Source: https://junglewise.ai/threats/cve-2010-4344-exim-heap-based-buffer-overflow-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2022-03-25. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2010-4344 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2022-03-25

A heap-based buffer overflow exists in the string_vformat function in Exim's string.c. Remote attackers can exploit this via a crafted SMTP session involving multiple MAIL commands and large message headers to execute arbitrary code.

Technologies: [Exim](https://junglewise.ai/threats/technologies/exim). Vendors: [Exim](https://junglewise.ai/threats/vendors/exim).

## Quick answers

**Is CVE-2010-4344 exploited in the wild?** Yes. CVE-2010-4344 is known to be exploited in the wild, first recorded on 25 March 2022. Treat it as urgent.

**How severe is CVE-2010-4344?** Critical severity, with a CVSS score of 9.8, published 25 March 2022.

**Which products and versions are affected?** Exim Exim before 4.70.

**Is there a fix for CVE-2010-4344?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2010-4344 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2010-4344?** Check whether you run Exim. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Exim Exim before 4.70

## Timeline

- 2010-12-10: disclosed: Initial public disclosure and mailing list discussions.
- 2022-03-25: kev added: Added to CISA Known Exploited Vulnerabilities Catalog.
- 2022-03-25: exploited: Reported as exploited in the wild.

## Related threats

- [Exim SMTP smuggling in DATA phase rejection handling](https://junglewise.ai/threats/cve-2026-94057-exim-before-4-100-1-allows-smtp-smuggling-in-which-the-received)
- [Exim Proxy Protocol stack memory disclosure](https://junglewise.ai/threats/cve-2026-94056-exim-before-4-100-1-when-proxy-protocol-is-used-with-an-attacker)
- [Exim before 4.100.1, when certain non-default TLS settings are used with GnuTLS, has a use-after-free.](https://junglewise.ai/threats/cve-2026-94055-exim-before-4-100-1-when-certain-non-default-tls-settings-are)
- [Exim out-of-bounds write in Proxy Protocol v1](https://junglewise.ai/threats/cve-2026-94054-exim-before-4-100-1-when-proxy-protocol-is-used-with-an-attacker)
- [Exim privilege escalation in .forward pipe transport force_command](https://junglewise.ai/threats/cve-2026-66141-exim-privilege-escalation-in-forward-pipe-transport-force-command)