CVE-2002-0006 in XChat
Summary
by MITRE
XChat 1.8.7 and earlier, including default configurations of 1.4.2 and 1.4.3, allows remote attackers to execute arbitrary IRC commands as other clients via encoded characters in a PRIVMSG command that calls CTCP PING, which expands the characters in the client response when the percascii variable is set.
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Analysis
by VulDB Data Team • 12/17/2024
This vulnerability exists in XChat versions 1.8.7 and earlier, including the default configurations of versions 1.4.2 and 1.4.3, representing a critical security flaw that enables remote code execution through manipulated IRC protocol communications. The vulnerability specifically targets the handling of PRIVMSG commands containing encoded characters that trigger CTCP PING functionality, creating a dangerous condition where attacker-controlled input can be executed as commands within the IRC client environment. The flaw exploits the client's response mechanism when the percascii variable is enabled, allowing attackers to manipulate character encoding in ways that bypass normal security restrictions and execute arbitrary code with the privileges of other connected clients. This represents a classic command injection vulnerability that leverages the IRC protocol's CTCP (Client-to-Client Protocol) extensions to achieve unauthorized access and execution.
The technical implementation of this vulnerability occurs through the manipulation of PRIVMSG command parameters that contain encoded characters designed to trigger CTCP PING responses. When the percascii variable is set in the client configuration, the application processes these encoded characters in a manner that expands them into executable command sequences within the client's response handling mechanism. This creates a condition where legitimate IRC protocol features become attack vectors, allowing malicious actors to inject commands that execute within the context of other users' IRC sessions. The vulnerability specifically exploits the client's interpretation of percent-encoded characters and their expansion during CTCP PING processing, effectively creating a code execution path that bypasses normal input validation and sanitization measures.
The operational impact of this vulnerability extends beyond simple command execution to encompass full compromise of IRC client sessions and potential network-level attacks. An attacker could leverage this vulnerability to execute arbitrary commands on behalf of other users, potentially gaining access to sensitive information, manipulating chat sessions, or using the compromised clients as launching points for further attacks within the IRC network. The vulnerability affects not just individual user sessions but could potentially enable attackers to control multiple client connections simultaneously, especially in environments where multiple users share the same IRC network or channel. This makes it particularly dangerous in collaborative environments or when used as part of a broader attack strategy against IRC infrastructure.
This vulnerability aligns with CWE-77 and CWE-94 categories, representing command injection and code execution flaws that occur when untrusted data is incorporated into command execution contexts without proper validation or sanitization. The ATT&CK framework categorizes this under T1059.001 for command and scripting interpreter execution, as the vulnerability enables attackers to execute commands through legitimate client interfaces. The flaw demonstrates poor input validation and sanitization practices in the IRC client's handling of encoded characters, particularly within CTCP protocol extensions. Organizations using XChat or similar IRC clients should immediately implement security patches or upgrades to address this vulnerability. Mitigation strategies include disabling the percascii variable, implementing strict input validation for PRIVMSG commands, and monitoring IRC network traffic for suspicious CTCP PING patterns. The vulnerability also highlights the importance of proper security configuration management and the need for regular security updates in client applications that handle network communications.