Improper S/MIME Certificate Validation in SEPPmail Secure Email Gateway
CVE-2026-2748

7.8HIGH

Key Information:

Vendor

Seppmail

Status
Secure Email Gateway
Vendor
CVE Published:
4 March 2026

What is CVE-2026-2748?

The SEPPmail Secure Email Gateway prior to version 15.0.1 is vulnerable due to improper validation of S/MIME certificates associated with email addresses that contain whitespace characters. This flaw enables attackers to perform signature spoofing, potentially undermining the integrity of email communications.

Affected Version(s)

Secure Email Gateway 0 < 15.0.1

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
.