Description
Multiple buffer overflows in Exim before 4.43 may allow attackers to execute arbitrary code via (1) an IPv6 address with more than 8 components, as demonstrated using the -be command line option, which triggers an overflow in the host_aton function, or (2) the -bh command line option or dnsdb PTR lookup, which triggers an overflow in the dns_build_reverse function.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 4 | exim +3 | 4.43-1.RHEL4.3 | RHSA-2005:025 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Exploit-DB 2
- Exim 4.41 - 'dns_build_reverse' Local Read Emails EDB-1009 · local · May 25, 2005 · verified
- Exim 4.41 - 'dns_build_reverse' Local Buffer Overflow EDB-756 · local · Jan 15, 2005 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 3
- RHSA-2005:025 Red Hat Security Advisory: exim security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-635-1 exim - buffer overflow Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-637-1 exim-tls - buffer overflow Debian Security (DSA / DLA) · Mar 9, 2026
References
- 20050107 Exim host_aton() Buffer Overflow Vulnerability third-party-advisory
- VU#132992 third-party-advisory
- DSA-635 vendor-advisory
- http://ftp6.us.freebsd.org/pub/mail/exim/ChangeLogs/ChangeLog-4.44
- DSA-637 vendor-advisory
- 20050114 Exim dns_buld_reverse() Buffer Overflow Vulnerability third-party-advisory
- RHSA-2005:025 vendor-advisory
- GLSA-200501-23 vendor-advisory
- [exim] 20050104 2 smallish security issues mailing-list
- oval:org.mitre.oval:def:10347 vdb-entry signature