CVE-2026-29143

Critical

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.

SeverityCritical

CVSS9.1

Exploit probability—

ProductSeppmail Secure Email Gateway

PublishedApr 2, 2026

First seenApr 2, 2026

Weakness typeCWE-20Improper input validation

How to fix

Update

seppmail secure_email_gateway15.0.3 or later

Vendor advisories

downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503

Affected products

Product	Affected versions	Fixed in
seppmail secure_email_gateway	v < 15.0.3	15.0.3

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