CVE-2026-29140
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedSEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceSEPPmail Secure Email Gateway before version 15.0.3 contains a certificate substitution vulnerability in its S/MIME signature handling. An attacker can add attacker-controlled certificates to S/MIME signatures, which then get used for future encryption to victims, enabling the attacker to intercept or decrypt encrypted communications.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 15.0.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify SEPPmail Secure Email Gateway versionLocate the installed version of SEPPmail Secure Email Gateway in the system documentation, admin interface, or by running the product's version command. Common locations include the web-based admin panel or the output of a version query tool provided by SEPPmail.Affected if The installed version is any version before 15.0.3 (for example, 15.0.2, 15.0.1, 14.x, or earlier).
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Confirm S/MIME processing is enabledAccess the SEPPmail admin interface or configuration files and verify whether S/MIME signature handling or S/MIME encryption functionality is active. Look for settings related to S/MIME processing, certificate handling for signed emails, or email encryption policies.Affected if S/MIME processing is enabled and the product version is before 15.0.3.
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Review S/MIME certificate storageInspect the certificate store or configuration area where S/MIME certificates are maintained. Check for any unexpected, added, or modified certificates that were not explicitly imported by administrators. Look for certificates with unfamiliar issuers, unusual key sizes, or recent modification timestamps.Affected if Unexpected certificates exist in the S/MIME certificate storage and the version is before 15.0.3.
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Audit S/MIME-related log filesReview SEPPmail log files for S/MIME operations, particularly entries indicating certificate imports, signature verifications, or certificate substitution events. Look for log messages that suggest attacker-controlled certificates were processed.Affected if Logs show certificate injection or unauthorized certificate import events, and the version is before 15.0.3.
A user is affected if SEPPmail Secure Email Gateway is running any version before 15.0.3 with S/MIME functionality enabled, or if unexpected certificates are found in the S/MIME configuration.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped15.0.3
Upgrade SEPPmail Secure Email Gateway to version 15.0.3 or later to remediate the certificate injection vulnerability in S/MIME processing.
15.0.3
- Obtain the fixed version 15.0.3 from the official vendor download source at downloads.seppmail.com
- Review the upgrade documentation provided with the release
- Back up the current configuration and certificate store before upgrading
- Install version 15.0.3 following the vendor's documented upgrade procedure
- After upgrade, verify that S/MIME certificate validation is functioning correctly and that the system rejects certificates not properly validated
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-29140 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-29140 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data