CVE-2026-29143
Received Received - Intake
S/MIME Authentication Bypass in SEPPmail Gateway Before

Publication date: 2026-04-02

Last updated on: 2026-04-16

Assigner: Switzerland Government Common Vulnerability Program

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.
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Meta Information
Published
2026-04-02
Last Modified
2026-04-16
Generated
2026-06-16
AI Q&A
2026-04-02
EPSS Evaluated
2026-06-15
NVD
CVE-2026-29143
EUVD
EUVD-2026-18166
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
seppmail secure_email_gateway to 15.0.3 (exc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
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Executive Summary

This vulnerability affects SEPPmail Secure Email Gateway versions before 15.0.3. It occurs because the software does not properly authenticate the inner message of S/MIME-encrypted MIME entities. As a result, an attacker can manipulate or control trusted email headers within these encrypted messages.

Impact Analysis

The vulnerability allows an attacker to control trusted headers in S/MIME-encrypted emails, which can lead to spoofing or manipulation of email content that is normally trusted. This could result in unauthorized actions, misinformation, or bypassing security controls that rely on these headers.

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