by Kastro
Paper/Archive/CVE-2026-29143

CVE-2026-29143

SEPPmail Secure Email Gateway — S/MIME Decryption Impersonation

EPSS 0.3%CVSS 9.1
critical.is priorityof 100
31
CVSS 9.1 (NVD)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 16.4.164 × 203.3No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
Secure Email Gateway< 15.0.315.0.3CNA

Scores by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
NCSC.ch (CNA)7.8CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: partial

References

refdownloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503