CVE-2026-27441

CriticalRCE

Published: 04 March 2026

Published

04 March 2026

Modified

05 March 2026

KEV Added

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Patch

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CVSS Score v4 9.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:L/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 0.0031 22.6th percentile

Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-27441 is a critical-severity OS Command Injection (CWE-78) vulnerability in Seppmail Seppmail. Its CVSS base score is 9.5 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 22.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Deeper analysis

CVE-2026-27441 is a critical vulnerability in SEPPmail Secure Email Gateway versions before 15.0.1, where the software insufficiently neutralizes the PDF encryption password. This flaw enables OS command injection, classified under CWE-78. The issue carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), reflecting its high severity due to network accessibility, low attack complexity, and lack of prerequisites like privileges or user interaction.

An unauthenticated remote attacker can exploit this vulnerability over the network by crafting malicious input involving the PDF encryption password. Successful exploitation grants arbitrary OS command execution on the affected gateway, potentially leading to complete system compromise with high impacts on confidentiality, integrity, and availability.

The vendor's extended release notes for version 15.0 detail the vulnerability disclosure and mitigation at https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure, recommending an upgrade to SEPPmail Secure Email Gateway version 15.0.1 or later to address the issue.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-9377

Vulnerability details

SEPPmail Secure Email Gateway before version 15.0.1 insufficiently neutralizes the PDF encryption password, allowing OS command execution.

CWE(s): CWE-78

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1059.004 Unix Shell Execution

Adversaries may abuse Unix shell commands and scripts for execution.

attack.mitre.org →

Why these techniques?

OS command injection (CWE-78) in public-facing SEPPmail gateway directly enables remote unauthenticated RCE via Unix shell (T1059.004) and exploitation of public-facing apps (T1190).

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