What’s Vulnerable › Vulnerabilities

CVE-2026-29143: S/MIME Decryption Impersonation

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-02 · updated 2026-10-26
• Weakness: CWE-20

Description

SEPPmail Secure Email Gateway before version 15.0.3 does not properly authenticate the inner message of S/MIME-encrypted MIME entities, allowing an attacker to control trusted headers.

Affected products

• SEPPmail Secure Email Gateway: before 15.0.3 — fixed in 15.0.3

How to fix

Upgrade to a fixed version: SEPPmail Secure Email Gateway 15.0.3. Check the vendor advisory for mitigations.

References

• https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503

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