CVE-2026-103431 in colmux
Summary
by MITRE • 10/01/2026
colmux in collectl before 4.3.20.2 does not sanitize ANSI/VT100 terminal escape sequences in data received from remote collectl instances before displaying it, allowing a local user on a monitored host to inject escape sequences into the terminal of an operator running colmux, via a crafted process name (argv[0]).
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified as CVE-2019-15683 represents a significant security flaw within collectl versions prior to 4.3.20.2, specifically affecting the colmux utility which serves as a multiplexer for collecting system performance data from remote hosts. The core technical deficiency lies in the failure of colmux to properly sanitize ANSI or VT100 terminal escape sequences found within input data received from connected collectl instances before rendering that information on the operator's display interface. This lack of sanitization creates an injection vector where malicious actors can manipulate how text is interpreted by the terminal emulator, leading to unintended side effects beyond simple visual corruption.
From a technical perspective, this flaw exploits the way modern terminals interpret control characters embedded within standard output streams. By crafting specific process names that include ANSI escape sequences as part of argv[0], an attacker can inject commands directly into the terminal session running colmux. When the operator views the collected data, these injected sequences are executed by the terminal emulator rather than being displayed as literal text. This mechanism allows for a wide range of potential exploits depending on the capabilities supported by the specific terminal software in use, including cursor manipulation, color scheme changes, and potentially more severe interactions if the terminal supports advanced features like hyperlinks or shell escapes.
The operational impact is primarily driven by the requirement that an attacker must have local access to one of the monitored hosts running a compromised collectl instance. While this restricts the attack surface compared to remote code execution vulnerabilities, it remains critical in environments where system administrators rely on centralized monitoring dashboards for real-time visibility into server health and performance metrics. A successful exploitation could lead to visual spoofing attacks, where an attacker disguises malicious output as legitimate system data, potentially misleading operators during incident response or routine maintenance activities. Furthermore, depending on the terminal configuration, there is a risk of arbitrary command execution if the injected sequences trigger shell escapes or other interactive features enabled within the specific terminal environment.
This vulnerability aligns with CWE-16 known as Configuration Error and more specifically CWE-79 which covers Improper Neutralization of Input During Web Page Generation although in this context it applies to local application output rather than web pages, often categorized under CWE-83 for Command Injection via Terminal Escape Sequences. In terms of the MITRE ATT&CK framework, this behavior is consistent with techniques involving Display Manipulation and potentially Defense Evasion through visual obfuscation or spoofing. The attack vector leverages Local Privileges to achieve its goals, making it a concern primarily within trusted internal networks where lateral movement has already occurred but before privilege escalation takes place.
To mitigate this risk, organizations should immediately upgrade collectl to version 4.3.20.2 or later, which includes patches for the colmux component to properly sanitize incoming data streams and strip out dangerous escape sequences before rendering them. In environments where upgrading is not immediately feasible, administrators can implement input validation filters at the application level if custom modifications are possible, though this is less reliable than a vendor-patched solution. Additionally, restricting access to monitoring tools like collectl to only authorized personnel with local administrative privileges reduces the likelihood of an attacker gaining the necessary foothold on monitored hosts. Regular security audits and penetration testing focused on input validation in system administration utilities can help identify similar weaknesses before they are exploited in production environments.