TI-2026-23278 Aliases CVE-2026-29140 GHSA-mmr3-c33j-h2f2

S/MIME Signature Additional Certificate

LOW 38CWE-295Published 2026-04-02 · Updated 2026-04-02

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Spoofing
Confidentiality · integrity · availability: None · Low · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-295.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00122 2nd percentileScored 2026-11-07

Fix Fixed Secure Email Gateway (SEPPmail): 15.0.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
SEPPmail	Secure Email Gateway	before 15.0.3	15.0.3	Patch available	CNA

Secure Email Gateway VendorSEPPmail Affected before 15.0.3 Fixed in 15.0.3 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:seppmail:secure_email_gateway::::::::	before 15.0.3	Vulnerable	SEPPmail

cpe:2.3:a:seppmail:secure_email_gateway:*:*:*:*:*:*:*:* Versions before 15.0.3 Vulnerable ·SEPPmail

Remediation

Fix · CNA Secure Email Gateway (SEPPmail) Fixed in 15.0.3

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-04-02
SEPPmail Secure Email Gateway 15.0.3
14 records Highest priority Priority MEDIUM 2 MEDIUM, 12 LOW
Other records, highest priority first
- TI-2026-23281 S/MIME Decryption ImpersonationPriority MEDIUM 40
- TI-2026-23277 GINA State Confusion Account TakeoverPriority MEDIUM 40
- TI-2026-23282 Unicode Subject TagsPriority LOW 39
Show all 14 records →

Timeline

2026-10-02 Threatist record created from CVE-2026-29140
2026-10-03 Alias added: GHSA-mmr3-c33j-h2f2

References

Other 1

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

TI-2026-23281 S/MIME Decryption Impersonation CVSS 4.0HIGH 7.8
TI-2026-23277 GINA State Confusion Account Takeover CVSS 4.0HIGH 7.8
TI-2026-23282 Unicode Subject Tags CVSS 4.0HIGH 7.8
TI-2026-23279 Bounded Subject Tag Sanitization CVSS 4.0HIGH 7.7
TI-2026-23270 ESWmail-Verify Bypass CVSS 4.0MEDIUM 6.3
TI-2026-23276 PGP Decryption Sender LDAP Injection CVSS 4.0MEDIUM 6.3

See all 13 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences