Cyber Resilience

CVE-2026-27849

CriticalRCE

Published: 25 February 2026

Published
25 February 2026
Modified
15 April 2026
KEV Added
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Patch
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CVSS Score v3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0031 23.0th percentile
Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-27849 is a critical-severity OS Command Injection (CWE-78) vulnerability in Syss (inferred from references). 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 23.0th 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-2026-27849 is a critical OS command injection vulnerability (CWE-78) stemming from missing neutralization of special elements in the update functionality of a TLS-SRP connection, which is used for configuring devices inside a mesh network. Assigned 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), it affects specific firmware versions: MR9600 1.0.4.205530 and MX4200 1.0.13.210200. Published on 2026-02-25, this flaw allows arbitrary OS command execution on impacted devices.

A remote, unauthenticated attacker can exploit the vulnerability over the network with low complexity and no user interaction required. By injecting malicious commands via the TLS-SRP update mechanism, the attacker can achieve high-impact compromise, including unauthorized access to sensitive data (C:H), modification of system behavior (I:H), and disruption of device operations (A:H), potentially leading to full control over the affected mesh network devices.

The SYSS advisory provides further details on the issue, available at https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2025-011.txt.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability details

Due to missing neutralization of special elements, OS commands can be injected via the update functionality of a TLS-SRP connection, which is normally used for configuring devices inside the mesh network. This issue affects MR9600: 1.0.4.205530; MX4200: 1.0.13.210200.

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?

Remote unauthenticated OS command injection (CWE-78) in network-exposed update functionality directly enables T1190 for initial access and T1059.004 for arbitrary Unix shell command execution on the device.

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

CVEs Like This One

CVE-2018-25115Shared CWE-78
CVE-2025-24382Shared CWE-78
CVE-2026-29058Shared CWE-78
CVE-2024-57016Shared CWE-78
CVE-2024-46484Shared CWE-78
CVE-2015-10145Shared CWE-78
CVE-2020-37002Shared CWE-78
CVE-2026-27848Shared CWE-78
CVE-2025-0356Shared CWE-78
CVE-2025-13942Shared CWE-78

Affected Assets

Syss
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inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match
prevent

Directly addresses the missing neutralization of special elements in the TLS-SRP update inputs to prevent OS command injection.

SI-2 Flaw Remediation good match
prevent

Requires monitoring, testing, and installation of firmware patches to remediate the command injection vulnerability in affected MR9600 and MX4200 versions.

SI-9 Information Input Restrictions partial match
prevent

Restricts inputs to the update functionality to permitted types and formats, mitigating injection of malicious OS commands via disallowed special elements.

References