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 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0006 20.1th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-27441 is a critical-severity OS Command Injection (CWE-78) vulnerability in Seppmail Seppmail. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 20.1th 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).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Requires timely remediation of the specific command injection flaw via patching to SEPPmail version 15.0.1 or later.

SI-10 Information Input Validation good match

prevent

Enforces validation and neutralization of untrusted inputs like the PDF encryption password to block OS command injection.

AC-6 Least Privilege partial match

prevent

Limits damage from successful command injection by restricting the gateway process to least privilege necessary for operations.

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 v18.1

NVD Description

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

Deeper analysisAI

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.