CVE-2026-29140 S/MIME Signature Additional Certificate
Attackers can inject malicious certificates into S/MIME signatures, enabling unauthorized decryption of future emails sent to victims.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-29140?
CVE-2026-29140 is a high-severity vulnerability in SEPPmail Secure Email Gateway, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-295
Which versions are affected by CVE-2026-29140?
It affects 1 product.
Products include Seppmail Secure Email Gateway.
How do I fix CVE-2026-29140?
No fix has been published for CVE-2026-29140 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-29140 being exploited?
There is no known exploitation of CVE-2026-29140 in the wild and no public exploit code.
Other vulnerabilities in SEPPmail Secure Email Gateway
Sources
Also known as GHSA-mmr3-c33j-h2f2.