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

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: yes — in CISA KEV since 2022-03-25
EPSS: 71.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2010-12-14 · updated 2026-06-16
Weakness: CWE-787

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.

Affected products

Canonical Ubuntu Linux: 6.06, 8.04, 9.10
Debian Linux: 5.0
Exim: before 4.70 — fixed in 4.70
Opensuse: 11.1, 11.2, 11.3

How to fix

Upgrade to a fixed version: Exim 4.70. Check the vendor advisory for mitigations.

References

http://atmail.com/blog/2010/atmail-6204-now-available/
http://bugs.exim.org/show_bug.cgi?id=787
http://git.exim.org/exim.git/commit/24c929a27415c7cfc7126c47e4cad39acf3efa6b
http://lists.exim.org/lurker/message/20101210.164935.385e04d0.en.html
http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00003.html
http://openwall.com/lists/oss-security/2010/12/10/1
http://secunia.com/advisories/40019
http://secunia.com/advisories/42576
http://secunia.com/advisories/42586
http://secunia.com/advisories/42587
http://secunia.com/advisories/42589

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