CVE-2026-29143 HIGH

CVE-2026-29143: S/MIME Decryption Impersonation

Vendor Seppmail
Product Secure Email Gateway
Weakness CWE-20 · Input validation
Published April 2, 2026
Last update April 2, 2026
View on NVD All CVEs

CVSS base score

7.8/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 2, 2026 CVE published
April 2, 2026 Record updated