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Secure Email Gateway CVE-2026-29143

| EUVDEUVD-2026-18166 HIGH
Improper Input Validation (CWE-20)
2026-04-02 NCSC.ch GHSA-q7v7-25qx-fcxf
Information Disclosure Secure Email Gateway
7.8
CVSS 4.0 · NVD
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Severity by source

NVD PRIMARY
7.8 HIGH
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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

7
Re-analysis Queued
Apr 16, 2026 - 19:07 vuln.today
cvss_changed
Analysis Updated
Apr 16, 2026 - 06:08 EUVD-patch-fix
executive_summary
Re-analysis Queued
Apr 16, 2026 - 05:29 backfill_euvd_patch
patch_released
Patch available
Apr 16, 2026 - 05:29 EUVD
15.0.3
EUVD ID Assigned
Apr 02, 2026 - 09:00 euvd
EUVD-2026-18166
Analysis Generated
Apr 02, 2026 - 09:00 vuln.today
CVE Published
Apr 02, 2026 - 08:49 nvd
HIGH 7.8

DescriptionCVE.org

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.

AnalysisAI

SEPPmail Secure Email Gateway before version 15.0.3 fails to properly authenticate inner messages within S/MIME-encrypted MIME entities, permitting attackers to manipulate trusted email headers and potentially forge message authenticity. This vulnerability affects the cryptographic validation layer of the gateway, enabling header injection attacks that could deceive users about message origin or content integrity. No CVSS score, EPSS data, or active exploitation confirmation is available in current intelligence.

Technical ContextAI

S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for digitally signing and encrypting email messages using public key cryptography. The vulnerability stems from improper authentication of the inner MIME message structure within encrypted entities, classified under CWE-20 (Improper Input Validation). SEPPmail Secure Email Gateway, identified via CPE cpe:2.3:a:seppmail:secure_email_gateway, is an enterprise email security appliance that processes and validates email messages. The flaw allows an attacker to craft a malicious S/MIME-encrypted message where the inner message headers are not cryptographically bound to the signature verification, creating a gap between the encrypted outer layer and the authenticated inner content. This is distinct from standard S/MIME parsing and reflects a gap in the authentication chain during message decryption and header extraction.

RemediationAI

Vendor-released patch: SEPPmail Secure Email Gateway version 15.0.3 and later. Organizations should upgrade immediately to version 15.0.3 or any subsequent release. Detailed remediation steps and release notes are available in the official SEPPmail advisory at https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503. No interim workarounds are documented; patching is the primary remediation path.

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CVE-2026-29143 vulnerability details – vuln.today
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