Vulnerability · Published Apr 2, 2026 · Assigned by NCSC.ch
CVE-2026-29140S/MIME Signature Additional Certificate
High 7.7
In plain English
A high-severity improper certificate validation in Secure Email Gateway from SEPPmail. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities).
Severity (CVSS 4.0)7.7High
Exploit odds (30 days)0.1%top 98.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| SEPPmail | Secure Email Gateway | 0 – before 15.0.3 |
Weakness: CWE-295 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:N/SA:N