Authentication Flaw in SEPPmail Secure Email Gateway Affects Email Security
CVE-2026-29143

7.8HIGH

Key Information:

Vendor

Seppmail

Status
Secure Email Gateway
Vendor
CVE Published:
2 April 2026

What is CVE-2026-29143?

The SEPPmail Secure Email Gateway, before version 15.0.3, suffers from an authentication flaw that affects the inner message handling of S/MIME-encrypted MIME entities. This vulnerability could allow attackers to manipulate trusted headers, potentially leading to unauthorized access or email spoofing. Organizations utilizing this email gateway must prioritize updating to the latest version to mitigate exposure to this security threat.

Affected Version(s)

Secure Email Gateway 0 < 15.0.3

References

https://downloads.seppmail.com/extrelnotes/150/ERN15.0.ht...
release-notes

CVSS V4

Score:
7.8
Severity:
HIGH
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Andris Suter-Dörig
Matteo Scarlata
Kenny Paterson
.