CVE-2011-1496 in tmux
Summary
by MITRE
tmux 1.3 and 1.4 does not properly drop group privileges, which allows local users to gain utmp group privileges via a filename to the -S command-line option.
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Analysis
by VulDB Data Team • 09/04/2024
The vulnerability identified as CVE-2011-1496 affects tmux versions 1.3 and 1.4, representing a critical privilege escalation flaw that stems from improper privilege management during application execution. This issue resides within the core privilege dropping mechanism of the terminal multiplexer, where the software fails to correctly relinquish group privileges after initialization. The vulnerability specifically manifests when users provide a filename argument through the -S command-line option, creating a pathway for local attackers to exploit the flawed privilege handling process.
The technical flaw in tmux stems from inadequate implementation of privilege separation mechanisms, where the application does not properly execute the setgroups() system call or similar privilege dropping functions that would normally transition the process from elevated group privileges back to standard user groups. This misconfiguration allows the application to maintain membership in the utmp group, which typically holds elevated permissions necessary for managing system session information. The vulnerability is categorized under CWE-250 as "Execute Code with Unnecessary Privileges" and aligns with ATT&CK technique T1068 which covers "Local Privilege Escalation" through improper privilege management.
From an operational impact perspective, this vulnerability enables local users to escalate their privileges to gain access to utmp group permissions, which can provide access to system session tracking information and potentially allow for session hijacking or modification of user login records. The exploitation requires local system access and involves crafting a specific filename argument to the -S option, making it a local privilege escalation vector rather than a remote attack. Attackers can leverage this to potentially access sensitive session data, manipulate login records, or establish persistent access through modified session tracking mechanisms.
Mitigation strategies for CVE-2011-1496 involve immediate patching of tmux installations to versions that properly implement privilege dropping mechanisms. System administrators should ensure all tmux instances are updated to versions 1.5 or later where this vulnerability has been addressed through proper implementation of setgroups() and related privilege management functions. Additionally, implementing proper access controls and monitoring for unauthorized tmux usage can help detect potential exploitation attempts. The vulnerability demonstrates the importance of proper privilege separation in security-critical applications and highlights the need for thorough security testing of privilege management code paths. Organizations should also consider implementing principle of least privilege principles for tmux usage and regularly audit session management configurations to prevent similar privilege escalation vulnerabilities from being exploited in other applications.