CVE-2026-29143

CRITICALNVD 9.19.1—

9.1

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.

CVSS v3: 9.1
EG Score: 9.1(medium)
EPSS: 18.6%
KEV: Not listed

Published

April 2, 2026

Last Modified

April 16, 2026

Advisory Details (1)

Auto-updated May 20, 2026

No patch confirmed yet.

generic

15.0.4.3 Hotfix Release

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

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-20Improper Input Validation

Data Freshness Timeline

(refreshed 15× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-31 22:30 UTCepss_batch
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2026-05-26 07:18 UTCepss_batch
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2026-05-20 22:38 UTCepss_batch
2026-05-20 22:38 UTCepss_batch

Frequently asked(5)

What is CVE-2026-29143?

CVE-2026-29143 is a critical vulnerability published on April 2, 2026. 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.

When was CVE-2026-29143 disclosed?

CVE-2026-29143 was first published in the National Vulnerability Database on April 2, 2026, with the most recent update on April 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-29143 actively exploited?

CVE-2026-29143 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 18.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-29143?

CVE-2026-29143 has a CVSS v3 base score of 9.1 (NVD).

How do I remediate CVE-2026-29143?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-29143, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2026-29143

📅 Published

🔄 Last Modified

📋 Advisory Details (1)

15.0.4.3 Hotfix Release

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2026-29143?

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Frequently asked(5)

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