CVE-2006-0745 in X11
Summary
by MITRE
X.Org server (xorg-server) 1.0.0 and later, X11R6.9.0, and X11R7.0 inadvertently treats the address of the geteuid function as if it is the return value of a call to geteuid, which allows local users to bypass intended restrictions and (1) execute arbitrary code via the -modulepath command line option or (2) overwrite arbitrary files via -logfile.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 02/03/2025
The vulnerability described in CVE-2006-0745 represents a critical security flaw in the X.Org server implementation that affects versions 1.0.0 and later, including X11R6.9.0 and X11R7.0. This issue stems from a fundamental misunderstanding in the server's privilege handling mechanism where the system incorrectly interprets the memory address of the geteuid function as the actual return value of a function call. The geteuid system call is designed to return the effective user ID of the calling process, which serves as a crucial security mechanism for determining privilege levels and enforcing access controls. When the X.Org server treats the function address as a return value, it creates a dangerous condition where privilege checks become meaningless and can be easily bypassed.
The technical flaw manifests in how the X.Org server processes command line arguments, specifically the -modulepath and -logfile options. When a local user invokes the xorg-server with these parameters, the flawed privilege checking logic allows the attacker to manipulate the server's behavior in ways that should otherwise be restricted. The vulnerability operates under CWE-254, which categorizes it as a "Weakness in Privilege Management" where the system fails to properly validate or enforce privilege levels. The issue is particularly severe because it enables privilege escalation attacks that can result in arbitrary code execution or file modification, both of which are fundamental threats to system integrity and security.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it creates multiple attack vectors for malicious actors. Through the -modulepath option, attackers can potentially load malicious modules that execute arbitrary code with elevated privileges, effectively allowing them to gain root access to the system. The -logfile option presents an additional vector where attackers can overwrite arbitrary files on the system, potentially corrupting critical system files or creating backdoors for persistent access. These attack scenarios align with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation," and T1490, which covers "Inhibit System Recovery," as the vulnerability can be leveraged to compromise system integrity and availability.
The security implications of CVE-2006-0745 are particularly concerning because it affects the core X Window System server that runs on numerous Unix-like operating systems, including various Linux distributions and BSD implementations. This vulnerability demonstrates the critical importance of proper privilege management in system-level software and highlights the potential for seemingly minor coding errors to create catastrophic security flaws. The flaw essentially undermines the fundamental security model of the X server, which is designed to run with restricted privileges while maintaining proper access controls. Organizations running affected X.Org server versions should immediately implement mitigations including updating to patched versions, implementing strict file permissions, and monitoring for unauthorized access attempts to prevent exploitation of this vulnerability that could lead to complete system compromise.