CVE-2026-2748

S/MIME Certificate Subject Whitespace

SEPPmail Secure Email Gateway before version 15.0.1 improperly validates S/MIME certificates issued for email addresses containing whitespaces, allowing signature spoofing.

Affected

SEPPmail · Secure Email Gateway

CVSS v4.0 NCSC

7.8 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1 NVD

5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

0.20% chance of exploitation in the next 30 days, 9th percentile

Published

2026-03-04

Proof-of-concept exploits (1)

• lyducanh/atmnc0★ · 2026-04-01

Security advisories

• https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclo…

References

• CVE Record
• NVD entry

Related

• CVE-2025-15467