Cyber Posture

CVE-2026-6140

Critical

Published: 13 April 2026

Published
13 April 2026
Modified
27 April 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 0.0032 55.5th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Description

A vulnerability was found in Totolink A7100RU 7.4cu.2313_b20191024. This impacts the function UploadFirmwareFile of the file /cgi-bin/cstecgi.cgi of the component CGI Handler. Performing a manipulation of the argument FileName results in os command injection. The attack may be initiated remotely.…

more

The exploit has been made public and could be used.

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match
prevent

Directly mitigates OS command injection by requiring validation of the FileName argument in the UploadFirmwareFile CGI function to block malicious inputs.

SI-2 Flaw Remediation good match
prevent

Ensures timely identification, testing, and patching of the specific command injection flaw in the Totolink router's cstecgi.cgi handler.

RA-5 Vulnerability Monitoring and Scanning good match
detect

Supports vulnerability scanning to identify and prioritize OS command injection issues like CVE-2026-6140 in router firmware components.

Security SummaryAI

CVE-2026-6140 is an OS command injection vulnerability affecting the Totolink A7100RU router on firmware version 7.4cu.2313_b20191024. The issue resides in the UploadFirmwareFile function of the /cgi-bin/cstecgi.cgi CGI handler component, where manipulation of the FileName argument triggers command injection. This flaw is classified under CWE-77 (Command Injection) and CWE-78 (OS Command Injection).

The vulnerability enables remote exploitation by unauthenticated attackers (PR:N) with low attack complexity (AC:L) and no user interaction (UI:N), earning 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). Successful attacks can result in high impacts to confidentiality, integrity, and availability, allowing arbitrary OS command execution on the device.

VulDB advisories detail the vulnerability and note that an exploit has been made public, with a proof-of-concept available in a GitHub repository. Practitioners should monitor the Totolink vendor website for firmware updates or mitigation guidance, as no specific patches are referenced in the available advisories.

Details

CWE(s)
CWE-77CWE-78

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?

The vulnerability is an unauthenticated OS command injection in a public-facing CGI web interface on a router (T1190), enabling arbitrary Unix shell command execution (T1059.004).

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

References