CVE-2003-0063 in X11r6
Summary
by MITRE
The xterm terminal emulator in XFree86 4.2.0 and earlier allows attackers to modify the window title via a certain character escape sequence and then insert it back to the command line in the user s terminal, e.g. when the user views a file containing the malicious sequence, which could allow the attacker to execute arbitrary commands.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2003-0063 represents a significant security flaw in the xterm terminal emulator component of XFree86 versions 4.2.0 and earlier. This issue falls under the category of terminal emulation security vulnerabilities and specifically exploits the improper handling of escape sequences within terminal applications. The vulnerability is particularly concerning because it demonstrates how seemingly benign terminal features can be weaponized to execute malicious code, creating a sophisticated attack vector that leverages user interaction patterns.
The technical flaw resides in xterm's inadequate validation and sanitization of escape sequences, particularly those used for window title manipulation. When an attacker crafts a malicious escape sequence that modifies the terminal window title, this sequence can be embedded within files or displayed content that users subsequently view. The vulnerability exploits the fact that xterm does not properly sanitize or escape these sequences when they are processed back into the command line context, allowing the malicious escape codes to be interpreted as actual commands rather than mere formatting instructions. This creates a scenario where viewing a file containing the malicious sequence triggers the execution of arbitrary commands within the user's terminal session.
The operational impact of CVE-2003-0063 extends beyond simple command execution, as it enables attackers to manipulate terminal sessions in ways that can compromise user environments and potentially lead to full system compromise. The vulnerability operates through a sophisticated attack chain that requires user interaction, making it particularly dangerous in environments where users frequently view files or content from untrusted sources. The attack vector demonstrates how terminal emulators can become attack surfaces when they fail to properly isolate and validate escape sequence processing, potentially allowing attackers to execute commands with the privileges of the affected user. This vulnerability is particularly dangerous because it can be exploited through seemingly innocuous file viewing operations, making it difficult for users to recognize the security risk.
The security implications of this vulnerability align with CWE-15 (External Control of System or Configuration Setting) and can be mapped to ATT&CK technique T1059.007 (Command and Scripting Interpreter: Unix Shell) within the adversary tactics framework. The vulnerability essentially allows for command injection through terminal escape sequences, enabling attackers to bypass normal security controls and execute arbitrary code. Mitigation strategies should include immediate upgrades to patched versions of XFree86, implementation of terminal escape sequence filtering, and user education regarding the dangers of viewing untrusted files. Organizations should also consider implementing terminal session monitoring and validation of escape sequence processing to prevent similar vulnerabilities from being exploited in other terminal emulators or applications that handle similar escape sequences. The vulnerability serves as a critical reminder of the importance of proper input validation and sanitization in terminal applications, particularly those handling user-generated content or external data sources.