CVE-2003-0066 in rxvt
Summary
by MITRE
The rxvt terminal emulator 2.7.8 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 • 07/19/2019
The vulnerability identified as CVE-2003-0066 represents a critical security flaw in the rxvt terminal emulator version 2.7.8 and earlier, demonstrating a sophisticated form of command injection through terminal escape sequences. This vulnerability operates at the intersection of terminal emulation and command execution, creating a pathway for attackers to manipulate user environments through seemingly benign character sequences. The flaw specifically exploits the terminal's handling of escape sequences, which are standard control codes used to modify terminal behavior including cursor positioning, color changes, and window title modifications.
The technical implementation of this vulnerability relies on the improper validation and sanitization of escape sequences within the rxvt terminal emulator. When a user opens a file containing malicious escape sequences, the terminal processes these sequences and modifies the window title accordingly. However, the vulnerability occurs because the terminal emulator fails to properly sanitize these sequences before they are reinserted into the command line context. This creates a scenario where the window title modification, which should be purely cosmetic, becomes a vector for command injection. The escape sequences can be crafted to include command execution directives that are subsequently interpreted when the terminal processes the modified window title.
The operational impact of this vulnerability extends beyond simple command execution to encompass a broader category of security risks including potential privilege escalation and information disclosure. Attackers can craft malicious files containing escape sequences that, when viewed by unsuspecting users, execute arbitrary commands with the privileges of the affected user. This vulnerability particularly affects environments where users frequently open files from untrusted sources or where terminal emulators are used in automated processes. The attack vector is particularly insidious because it leverages user trust in terminal applications and can be concealed within normal file operations such as viewing text files, source code, or log files.
This vulnerability maps directly to CWE-74, which describes "Improper Neutralization of Special Elements in Output Used by a Downstream Component" and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript. The attack chain typically follows a pattern where an attacker places malicious escape sequences in files that users will open, such as configuration files, source code, or documentation. When the user opens these files, the terminal emulator processes the escape sequences, modifies the window title, and then reinserts the malicious content back into the command line context. This creates a command injection scenario where the attacker can execute arbitrary commands on the victim's system.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate patching and operational security measures. The most effective solution involves upgrading to rxvt terminal emulator versions 2.7.9 and later, which contain patches specifically addressing the escape sequence sanitization issue. Organizations should implement strict file validation policies, particularly for files containing escape sequences or special characters, and establish user education programs to raise awareness about potentially malicious file content. Additionally, implementing terminal security monitoring tools that can detect and block suspicious escape sequence patterns provides an additional layer of protection. System administrators should also consider restricting the execution of terminal emulators with known vulnerabilities in high-security environments and implementing network-based security controls that can detect and prevent the transmission of malicious escape sequences through network protocols.