S/MIME Decryption Impersonation

MITRE NVD CVE.ORG Print: PDF PDF

Summary

CVECVE-2026-29143
StatePUBLISHED
AssignerNCSC.ch
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-02 09:16:23 UTC
Updated2026-04-02 09:16:23 UTC
DescriptionSEPPmail 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.

Risk And Classification

Primary CVSS: v4.0 7.8 HIGH from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-20 | CWE-20 CWE-20 Improper Input Validation

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.8HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N/E:X/C...
4.0CNACVSS7.8HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Sub Conf.
Low
Sub Integrity
High
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA SEPPmail Secure Email Gateway affected 15.0.3 custom Not specified

References

ReferenceSourceLinkTags
downloads.seppmail.com/extrelnotes/150/ERN15.0.html [email protected] downloads.seppmail.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Andris Suter-Dörig (en)

CNA: Matteo Scarlata (en)

CNA: Kenny Paterson (en)

Additional Advisory Data

SourceTimeEvent
CNA2025-10-31T14:22:00.000ZVulnerability disclosed to SEPPmail
CNA2026-03-03T00:00:00.000ZVersion 15.0.3 released
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