CVE-2026-29143: Seppmail Secure Email Gateway

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

SEPPmail Secure Email Gateway before version 15.0.3 does not properly authenticate the inner message of S/MIME-encrypted MIME entities, allowing an attacker to control trusted headers.

Affected products

• Seppmail Secure Email Gateway: before 15.0.3 (fixed in 15.0.3)

Published 2026-04-02. Last modified 2026-06-17.