What is CVE-2026-29140?

CVE-2026-29140 is a medium-severity vulnerability in Seppmail Secure Email Gateway, classified under Improper Certificate Validation. CVSS score: 5.3/10. Published 2026-04-02.

How severe is CVE-2026-29140?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Seppmail Secure Email Gateway

CVE-2026-29140

SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures.

Vulnerability class: Improper Certificate Validation

EPSS: 0.001 (2.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

Affected products

Seppmail Secure Email Gateway — versions 0
Seppmail Secure_email_gateway

Weakness classification (CWE)

CWE-295 — Improper Certificate Validation

References

vulnerability@ncsc.ch (release-notes, Release Notes)

Frequently asked questions

What is CVE-2026-29140?: CVE-2026-29140 is a medium-severity vulnerability in Seppmail Secure Email Gateway, classified under Improper Certificate Validation. CVSS score: 5.3/10. Published 2026-04-02.
How severe is CVE-2026-29140?: Medium severity. CVSS v3 base score is 5.3 out of 10.