CVE-2011-0465 in X11
Summary
by MITRE
xrdb.c in xrdb before 1.0.9 in X.Org X11R7.6 and earlier allows remote attackers to execute arbitrary commands via shell metacharacters in a hostname obtained from a (1) DHCP or (2) XDMCP message.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability described in CVE-2011-0465 represents a critical command injection flaw within the xrdb utility of X.Org X11R7.6 and earlier versions. This issue stems from improper input validation in the xrdb.c component which processes hostname information obtained through network protocols. The vulnerability specifically affects systems that utilize DHCP or XDMCP (X Display Manager Control Protocol) for network configuration and display management. When these protocols transmit hostname data to the xrdb utility, the application fails to properly sanitize the input before using it in shell commands, creating an avenue for remote code execution.
The technical exploitation of this vulnerability occurs through the manipulation of hostname values within DHCP or XDMCP messages. Attackers can inject shell metacharacters such as semicolons, ampersands, or backticks into the hostname field, which are then processed by the xrdb utility without adequate sanitization. This flaw directly maps to CWE-78, which describes improper neutralization of special elements used in operating system commands, commonly known as OS command injection. The vulnerability exists because the application constructs shell commands by concatenating user-supplied hostname data directly into command strings, bypassing proper input validation and sanitization mechanisms.
From an operational standpoint, this vulnerability presents significant risks to networked X11 environments where DHCP or XDMCP services are actively used. Remote attackers can leverage this weakness to execute arbitrary commands with the privileges of the user running the xrdb utility, potentially leading to complete system compromise. The attack surface is particularly broad since XDMCP and DHCP are standard protocols used in enterprise environments for display management and network configuration. Systems that rely on these protocols for automatic hostname assignment or display manager communication become vulnerable to unauthorized code execution, potentially allowing attackers to establish persistent backdoors, escalate privileges, or exfiltrate sensitive data.
The impact of this vulnerability extends beyond simple command execution to encompass broader security implications for X11-based network environments. Organizations using older X.Org versions are particularly at risk since the flaw exists in the core display management utilities. The ATT&CK framework categorizes this vulnerability under T1059.007 for Command and Scripting Interpreter: Unix Shell, as it enables attackers to execute shell commands through legitimate system utilities. Mitigation strategies should focus on immediate patching of X.Org installations to version 1.0.9 or later, where the input sanitization issues have been addressed. Network segmentation and firewall rules that restrict DHCP and XDMCP traffic can provide temporary protection while patches are deployed. Additionally, implementing proper input validation and sanitization in all network-facing applications that process external hostname data will help prevent similar vulnerabilities from emerging in the future.