CVE-2003-0023 in rxvt
Summary
by MITRE
The menuBar feature in rxvt 2.7.8 allows attackers to modify menu options and execute arbitrary commands via a certain character escape sequence that inserts the commands into the menu.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2003-0023 represents a critical security flaw in the rxvt terminal emulator version 2.7.8 that stems from improper handling of character escape sequences within its menuBar functionality. This issue allows malicious actors to manipulate the terminal's menu options and subsequently execute arbitrary commands through carefully crafted escape sequences that are processed by the application. The vulnerability specifically targets the way rxvt interprets and processes escape codes that are typically used for terminal control and formatting, but in this case, the implementation fails to properly sanitize or validate input from these sequences before incorporating them into menu structures.
The technical exploitation of this vulnerability occurs through the manipulation of escape sequences that are normally used for terminal control operations. When rxvt processes these sequences, it fails to properly validate or sanitize the input data, allowing attackers to inject malicious commands that get embedded directly into the menu options. This creates a privilege escalation scenario where an attacker can potentially execute arbitrary code with the privileges of the user running the rxvt terminal. The flaw exists at the input validation layer where escape sequences containing command data are not properly filtered or escaped before being processed and displayed in the menuBar interface. This represents a classic buffer overflow vulnerability variant that operates on command injection rather than memory corruption, with the attack surface being the menu system rather than direct memory manipulation.
The operational impact of this vulnerability extends beyond simple command execution to potentially compromise entire terminal sessions and user environments. Since rxvt is commonly used in Unix-like systems and is often integrated into desktop environments, successful exploitation could allow attackers to gain unauthorized access to system resources, execute malicious payloads, or establish persistent access points through the compromised terminal application. The vulnerability affects users who have rxvt installed and are running applications that utilize its menuBar feature, potentially exposing them to remote code execution attacks. This type of vulnerability is particularly dangerous in multi-user environments where terminal emulators are frequently used for system administration tasks, as it could enable attackers to escalate privileges or access sensitive system information. The attack vector is particularly insidious because it leverages legitimate terminal functionality to deliver malicious payloads, making detection more challenging and allowing the vulnerability to persist longer in compromised systems.
Mitigation strategies for CVE-2003-0023 should focus on immediate patching of the affected rxvt version 2.7.8, as this represents the most effective solution to address the root cause of the vulnerability. System administrators should also implement network-level controls to restrict access to terminal applications that may be vulnerable, particularly in environments where untrusted users have access to terminal sessions. Input validation and sanitization measures should be implemented at the application level to ensure that escape sequences are properly filtered before being processed by the menuBar functionality. Additionally, users should be educated about the risks of executing untrusted code in terminal environments and the importance of keeping terminal applications updated with the latest security patches. From a compliance perspective, this vulnerability aligns with CWE-74 which covers "Improper Neutralization of Special Elements in Output Used by a Downstream Component," and it maps to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" where the malicious command execution occurs through legitimate terminal interfaces. Organizations should also consider implementing application whitelisting policies to prevent execution of unauthorized terminal applications that may contain similar vulnerabilities. The vulnerability demonstrates the importance of proper input validation in terminal applications and serves as a reminder that even seemingly benign features like menu systems can become attack vectors when proper security controls are not implemented.