CVE-2003-0022 in rxvt
Summary
by MITRE
The "screen dump" feature in rxvt 2.7.8 allows attackers to overwrite arbitrary files via a certain character escape sequence when it is echoed to a user s terminal, e.g. when the user views a file containing the malicious sequence.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2003-0022 resides within the rxvt terminal emulator version 2.7.8, specifically targeting its screen dump functionality. This flaw represents a classic case of improper input validation and privilege escalation through terminal escape sequences. The vulnerability manifests when the terminal processes character escape sequences that are designed to capture screen contents for dumping purposes, but fails to properly sanitize or validate the input before executing these operations. The flaw enables attackers to craft malicious escape sequences that, when processed by the terminal, can overwrite arbitrary files on the system where the vulnerable software is running.
The technical exploitation of this vulnerability occurs through the manipulation of escape sequences that are normally used for legitimate screen capture operations. When a user views a file containing these malicious sequences in the rxvt terminal, the software processes the escape codes without adequate validation, allowing an attacker to specify arbitrary file paths for overwriting. This represents a direct violation of proper input validation principles and demonstrates how terminal emulators can become attack vectors when they fail to properly sanitize escape sequence parameters. The vulnerability falls under the category of CWE-20, which describes improper input validation, and more specifically relates to CWE-77, which addresses command injection vulnerabilities through improper sanitization of special elements.
The operational impact of this vulnerability extends beyond simple file overwriting capabilities, as it can potentially enable attackers to compromise the integrity of the target system. An attacker who successfully exploits this vulnerability can overwrite critical system files, configuration files, or even user data, leading to potential system instability, data loss, or unauthorized access. The attack vector is particularly concerning because it requires no special privileges beyond being able to place malicious content in a file that will be viewed by a user with the vulnerable terminal emulator. This makes the vulnerability particularly dangerous in environments where users may encounter untrusted files or content, such as in web browsing scenarios or when processing email attachments. The vulnerability also aligns with ATT&CK technique T1059, which covers command and scripting interpreters, as the escape sequences essentially function as commands that can be interpreted by the terminal emulator.
The remediation for this vulnerability requires immediate patching of the rxvt terminal emulator to version 2.7.9 or later, which contains the necessary fixes for proper escape sequence validation. System administrators should also implement additional protective measures such as restricting access to potentially malicious files, monitoring terminal usage for suspicious activity, and ensuring that users are not viewing untrusted content in terminal environments. Organizations should consider implementing file integrity monitoring solutions to detect unauthorized file modifications that might result from exploitation of this vulnerability. The fix typically involves implementing proper bounds checking and validation of escape sequence parameters to prevent arbitrary file path specification, which aligns with security best practices for input sanitization and privilege separation in terminal applications.