CVE-2026-29143: SEPPmail Secure Email Gateway before version 15.0.3 does not properly authenticate the inner message of S/MIME

Q: How do I fix CVE-2026-29143?

secure email gateway: upgrade to 15.0.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-29143 being exploited?

CVE-2026-29143 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-29143 affect?

CVE-2026-29143 affects secure email gateway. Severity is critical (CVSS 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.

Q: How urgent is CVE-2026-29143?

Priority 41/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-29143 is a critical-severity flaw (CVSS 9.1) affecting secure email gateway. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 84%)
CISA exploited list	No
Weakness	CWE-20
Published	2026-04-02
Last modified	2026-10-26

Publisher (CNA): Switzerland Government Common Vulnerability Program · Vendor: seppmail

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-02 09:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

seppmail secure email gateway UPGRADE

Affected: < 15.0.3

Fixed in: 15.0.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy secure-email-gateway || rpm -q secure-email-gateway || secure-email-gateway --version

2. UPGRADE to 15.0.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade secure-email-gateway

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade secure-email-gateway

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-29143?

secure email gateway: upgrade to 15.0.3. Exact commands for each OS are on this page.

Is CVE-2026-29143 being exploited?

CVE-2026-29143 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-29143 affect?

CVE-2026-29143 affects secure email gateway. Severity is critical (CVSS 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.

How urgent is CVE-2026-29143?

Priority 41/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-29139 CRITICAL 9.8 UPGRADE SEPPmail Secure Email Gateway before version 15.0.3 allows account takeover by abusing GINA account initializa
CVE-2026-29133 CRITICAL 9.1 UPGRADE SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to upload PGP keys with UIDs that do no
CVE-2026-29131 HIGH 7.5 UPGRADE SEPPmail Secure Email Gateway before version 15.0.3 allows attackers with a specially crafted email address to
CVE-2026-29132 HIGH 7.5 UPGRADE SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker with access to a victim's GINA account
CVE-2026-29134 HIGH 7.5 UPGRADE SEPPmail Secure Email Gateway before version 15.0.3 allows an external user to modify GINA webdomain metadata

References

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