Cyber Resilience

CVE-2026-2748

High

Published: 04 March 2026

Published
04 March 2026
Modified
05 March 2026
KEV Added
—
Patch
—
CVSS Score v4 7.8 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
EPSS Score 0.0012 2.2th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-2748 is a high-severity Improper Certificate Validation (CWE-295) vulnerability in Seppmail Seppmail. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Email Spoofing (T1684.002); ranked at the 2.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability details

SEPPmail Secure Email Gateway before version 15.0.1 improperly validates S/MIME certificates issued for email addresses containing whitespaces, allowing signature spoofing.

CWE(s)
CWE-295

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1684.002 Email Spoofing Stealth
Adversaries may fake, or spoof, a sender’s identity by modifying the value of relevant email headers in order to establish contact with victims under false pretenses.
attack.mitre.org →
Why these techniques?

Improper S/MIME certificate validation directly enables forged email signatures, mapping to Email Spoofing.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Affected Assets

seppmail
seppmail
≤ 15.0.1

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SA-19 Component Authenticity
addresses: CWE-295

When certificates are used to establish component provenance, the control requires correct certificate validation procedures.

SC-17 Public Key Infrastructure Certificates
addresses: CWE-295

Mandates approved trust anchors and issuance policies, directly preventing acceptance of unvalidated or untrusted certificates.

SC-45 System Time Synchronization
addresses: CWE-295

Correct system time is required for proper enforcement of certificate notBefore/notAfter dates and time-based revocation checks.

References