CVE-2006-5969 in fvwm
Summary
by MITRE
CRLF injection vulnerability in the evalFolderLine function in fvwm 2.5.18 and earlier allows local users to execute arbitrary commands via carriage returns in a directory name, which is not properly handled by fvwm-menu-directory, a variant of CVE-2003-1308.
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Analysis
by VulDB Data Team • 04/27/2026
The CVE-2006-5969 vulnerability represents a critical command injection flaw within the fvwm window manager version 2.5.18 and earlier. This vulnerability specifically targets the evalFolderLine function where improper handling of carriage return characters creates an exploitable condition that allows local attackers to execute arbitrary commands. The flaw stems from insufficient input validation and sanitization within the fvwm-menu-directory component, which processes directory names and fails to properly escape or filter special characters including carriage returns and line feeds. The vulnerability operates through a classic CRLF injection attack vector where an attacker can manipulate directory names to inject command sequences that get executed by the vulnerable application.
This security weakness fundamentally exploits the lack of proper string sanitization in the window manager's menu generation process. When fvwm-menu-directory processes directory names containing carriage return characters, it fails to properly escape these control characters before using them in command execution contexts. The vulnerability is particularly dangerous because it allows local users to inject malicious payloads that can be executed with the privileges of the fvwm process, potentially leading to privilege escalation or complete system compromise. The flaw is categorized as a command injection vulnerability and aligns with CWE-77 and CWE-94, representing both command injection and improper input handling issues that enable arbitrary code execution.
The operational impact of CVE-2006-5969 extends beyond simple privilege escalation as it can enable attackers to gain unauthorized access to system resources, manipulate the desktop environment, or execute malicious code within the user's session. Since fvwm is a window manager that typically runs with user privileges, successful exploitation can allow attackers to execute commands in the context of the current user session, potentially leading to data exfiltration, system reconnaissance, or further attack escalation. The vulnerability is particularly concerning in multi-user environments where local users could leverage this flaw to compromise other users' sessions or gain access to sensitive information processed through the window manager.
Mitigation strategies for this vulnerability require immediate patching of the fvwm window manager to version 2.5.19 or later where the input sanitization issues have been addressed. System administrators should also implement proper input validation at the application level, ensuring that directory names and menu entries are properly sanitized before being processed by fvwm-menu-directory. Additionally, access controls should be reviewed to limit local user access to potentially vulnerable components, and monitoring should be implemented to detect unusual command execution patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in GUI applications and aligns with ATT&CK technique T1059 for command and scripting interpreter, emphasizing the need for robust sanitization of user inputs in desktop environments. Organizations should also consider implementing application whitelisting policies to restrict execution of potentially vulnerable components and ensure that all window managers and desktop environment components are regularly updated to prevent similar vulnerabilities from being exploited in the future.