CVE-2004-0400: Stack-based buffer overflow in Exim 4 before 4.33, when the headers_check_syntax option is enabled, allows...

Security readout for executives and security teams

This is an old Exim mail server flaw affecting Exim 4 before 4.33 when header syntax checking is enabled. A remote sender could crash the mail service and may be able to run code. The business risk is concentrated in legacy, internet-facing mail gateways still running affected versions or unpatched vendor packages. Exposure is likely limited to legacy Exim 4 deployments before 4.33, especially internet-facing mail transfer agents with headers_check_syntax enabled. Modern supported Exim packages should not be assumed affected without version confirmation. Prioritize remediation where Exim is exposed to the internet or handles business-critical mail. This is legacy exposure, but the remote crash and possible code execution impact justify prompt action if affected systems still exist. Mitigation focus: Upgrade Exim to 4.33 or a vendor-supported fixed package.; Review Debian DSA-501 and DSA-502 if using Debian packages.; Confirm whether headers_check_syntax is enabled on any legacy Exim hosts..

Prepared

Jun 30, 2026, 05:56 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.