CVE-2026-29143

CRITICAL

S/MIME Decryption Impersonation

Title source: cna

Description

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.

References (1)

[Release Notes] https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503

Scores

CVSS v3 9.1

EPSS 0.0005

EPSS Percentile 16.9%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Details

CWE

CWE-20

Status published

Products (2)

SEPPmail/Secure Email Gateway < 15.0.3

seppmail/secure_email_gateway < 15.0.3

Published Apr 02, 2026

Tracked Since Apr 02, 2026