CVE-2005-0764 in rxvt-unicode
Summary
by MITRE
Buffer overflow in command.C for rxvt-unicode before 5.3 allows remote attackers to execute arbitrary code via a crafted file containing long escape sequences.
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Analysis
by VulDB Data Team • 05/31/2019
The vulnerability identified as CVE-2005-0764 represents a critical buffer overflow flaw within the command.C component of rxvt-unicode terminal emulator versions prior to 5.3. This issue stems from inadequate input validation when processing escape sequences in terminal control commands, creating a pathway for remote code execution attacks. The vulnerability specifically affects the handling of escape sequences that are commonly used in terminal communication protocols to control display attributes, cursor positioning, and other terminal behaviors. When a maliciously crafted file containing excessively long escape sequences is processed by the vulnerable rxvt-unicode version, the application fails to properly bounds-check the input data, leading to memory corruption that can be exploited by attackers.
The technical exploitation of this vulnerability occurs through the manipulation of escape sequence parsing logic within the terminal emulator's command processing module. Escape sequences are control codes that begin with the escape character and are used to modify terminal behavior, including text formatting, color changes, and cursor movement. In rxvt-unicode versions before 5.3, the buffer allocated for storing these escape sequences was insufficient to handle unusually long sequences, causing a classic stack-based buffer overflow condition. This memory corruption can overwrite adjacent memory locations including return addresses and function pointers, enabling attackers to redirect program execution flow. The vulnerability is particularly dangerous because it can be triggered remotely through file-based attacks, where an attacker crafts a file containing malicious escape sequences that, when opened or processed by the vulnerable terminal emulator, execute arbitrary code with the privileges of the user running the application.
The operational impact of CVE-2005-0764 extends beyond simple privilege escalation to encompass potential system compromise and data exfiltration capabilities. Attackers exploiting this vulnerability can execute malicious code on target systems, potentially establishing persistent backdoors, escalating privileges, or accessing sensitive information stored within the compromised environment. The vulnerability affects any system running rxvt-unicode versions prior to 5.3, making it particularly concerning for environments where terminal emulators are widely used for command-line operations and system administration tasks. The remote exploitation capability means that attackers do not require direct access to the target system, as they can deliver malicious files through various vectors including email attachments, web downloads, or shared network resources. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and can be mapped to ATT&CK technique T1059 for command and scripting interpreter usage, as well as T1068 for exploit for privilege escalation.
Mitigation strategies for CVE-2005-0764 primarily focus on immediate patching and system hardening measures. The most effective solution involves upgrading to rxvt-unicode version 5.3 or later, where the buffer overflow vulnerability has been addressed through proper input validation and bounds checking. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious files, while monitoring for unusual file access patterns that might indicate exploitation attempts. Additional defensive measures include disabling automatic file execution for terminal files, implementing strict file type validation, and deploying intrusion detection systems that can identify suspicious escape sequence patterns. The vulnerability demonstrates the importance of input validation in terminal and console applications, where escape sequences represent a common attack surface for buffer overflow exploits. Security professionals should also consider implementing application whitelisting policies to restrict execution of untrusted terminal files and establish regular vulnerability assessment procedures to identify similar issues in other terminal emulators and console applications.