CVE-2003-0069 in PuTTY
Summary
by MITRE
The PuTTY terminal emulator 0.53 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 • 05/24/2019
The vulnerability identified as CVE-2003-0069 represents a significant security flaw in the PuTTY terminal emulator version 0.53 that exploits terminal escape sequence handling mechanisms. This vulnerability falls under the category of terminal emulation security issues and demonstrates how seemingly benign character sequences can be weaponized to manipulate user environments. The flaw specifically resides in how PuTTY processes escape sequences that modify terminal window properties, creating a pathway for malicious code injection through carefully crafted character sequences.
The technical implementation of this vulnerability exploits the terminal's handling of escape sequences, particularly those that modify window titles and other terminal attributes. When an attacker crafts a malicious escape sequence that modifies the window title, the vulnerable PuTTY version fails to properly sanitize or validate these sequences before processing them. This allows the attacker to inject specific character sequences that, when processed by the terminal, can alter the command line interface in ways that enable command execution. The vulnerability is particularly dangerous because it leverages the natural behavior of terminal emulators to process escape sequences, making it difficult to detect through traditional security measures.
The operational impact of this vulnerability extends beyond simple command injection, as it creates a sophisticated attack vector that can be exploited in various scenarios. An attacker could embed malicious escape sequences in files that users routinely view, such as log files, configuration files, or even simple text documents. When users open these files in terminals that process the escape sequences, the malicious commands would be executed within the user's terminal session. This attack model aligns with the attack pattern described in the ATT&CK framework under T1059 for command and scripting interpreter, specifically targeting the execution of commands through terminal manipulation. The vulnerability also relates to CWE-74, which describes improper neutralization of special elements in output used by a downstream component, and CWE-20, which covers input validation issues.
Mitigation strategies for this vulnerability should focus on both immediate defensive measures and long-term architectural improvements. Users should immediately upgrade to patched versions of PuTTY that properly sanitize escape sequences and implement proper input validation for all terminal attributes. Organizations should consider implementing terminal emulation policies that restrict the processing of certain escape sequences or implement additional layers of validation before any terminal attributes are modified. The vulnerability highlights the importance of proper input sanitization in terminal emulators and demonstrates how escape sequence handling can become a security vector when not properly validated. Security teams should also implement monitoring for unusual terminal attribute modifications and establish baseline behaviors for terminal emulators to detect potential exploitation attempts. This vulnerability serves as a reminder of the critical importance of validating all user-supplied data in terminal environments and the potential for seemingly innocuous character sequences to become sophisticated attack vectors.