CVE-2018-1000523 in topydo
Summary
by MITRE
topydo contains a CWE-20: Improper Input Validation vulnerability in ListFormatParser::parse, file topydo/lib/ListFormat.py line 292 as of d4f843dac71308b2f29a7c2cdc76f055c3841523 that can result in Injection of arbitrary bytes to the terminal, including terminal escape code sequences. This attack appear to be exploitable via The victim must open a todo.txt with at least one specially crafted line..
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Analysis
by VulDB Data Team • 03/28/2023
The vulnerability identified as CVE-2018-1000523 resides within the topydo library's ListFormatParser::parse method, specifically at line 292 in the file topydo/lib/ListFormat.py. This flaw represents a classic instance of CWE-20: Improper Input Validation, where the application fails to adequately validate or sanitize user-supplied input before processing it. The vulnerability stems from the library's handling of todo.txt files that contain specially crafted lines, creating a dangerous condition where arbitrary byte sequences can be injected directly into the terminal output. The security implications extend beyond simple data manipulation to include the potential execution of terminal escape code sequences, which can fundamentally alter terminal behavior and potentially enable sophisticated attack vectors.
The technical exploitation of this vulnerability requires a specific attack scenario where a victim must open a todo.txt file containing at least one maliciously crafted line. This dependency on user interaction makes the vulnerability a prime example of a user-facing attack vector that relies on social engineering or file manipulation. When the vulnerable parser encounters the specially crafted input, it fails to properly sanitize the data, allowing escape sequences and other terminal control codes to be interpreted and executed by the terminal emulator. The injection of terminal escape codes can lead to various malicious outcomes including screen manipulation, command execution, or even privilege escalation depending on the terminal environment and user permissions.
From an operational impact perspective, this vulnerability poses significant risks to users who regularly interact with todo.txt files through the topydo library. The attack surface is particularly concerning because todo.txt files are commonly used in productivity workflows and may be shared across teams or stored in accessible locations. The potential for arbitrary code execution through terminal escape sequences means that attackers could manipulate terminal displays, capture user input, or potentially execute commands with the privileges of the user running the application. This vulnerability directly impacts the principle of least privilege and can undermine the security posture of systems where such productivity tools are prevalent. The attack vector is particularly insidious because it requires minimal user interaction beyond simply opening a file, making it difficult to defend against through traditional user awareness training alone.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and sanitization within the ListFormatParser::parse method. The recommended approach includes thorough sanitization of input data to remove or escape terminal control characters before processing, implementing strict parsing rules that reject malformed input, and conducting regular security audits of input handling code paths. Organizations should also consider implementing file access controls and user education regarding the risks of opening untrusted todo.txt files. From a defensive standpoint, this vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution, as the escape sequences could potentially be used to execute terminal commands. Additionally, the vulnerability demonstrates the importance of proper input validation as outlined in CWE-20, emphasizing the need for robust sanitization routines in all user-facing input processing components. The fix should ensure that all terminal escape sequences are either properly neutralized or explicitly validated before being interpreted by the terminal emulator.