CVE-2017-17523 in LilyPond
Summary
by MITRE
lilypond-invoke-editor in LilyPond 2.19.80 does not validate strings before launching the program specified by the BROWSER environment variable, which allows remote attackers to conduct argument-injection attacks via a crafted URL, as demonstrated by a --proxy-pac-file argument.
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Analysis
by VulDB Data Team • 01/17/2023
The vulnerability identified as CVE-2017-17523 resides within the lilypond-invoke-editor component of LilyPond version 2.19.80, representing a critical security flaw that enables remote attackers to execute argument-injection attacks through improper input validation. This issue specifically targets the handling of strings before program execution, creating a dangerous pathway for malicious actors to manipulate system behavior through environment variable manipulation. The vulnerability manifests when the application fails to sanitize user-provided input before incorporating it into command-line arguments for programs specified by the BROWSER environment variable, thereby exposing the system to unauthorized command execution.
The technical flaw operates through a classic command injection vector where the lilypond-invoke-editor component directly incorporates user-supplied strings into system commands without adequate validation or sanitization. When a crafted URL containing malicious arguments is processed, the application passes these unvalidated inputs directly to the BROWSER environment variable's target program, allowing attackers to inject additional command-line arguments such as --proxy-pac-file. This behavior aligns with CWE-77 and CWE-88, which specifically address command injection vulnerabilities and argument injection flaws respectively, where insufficient input validation permits attackers to manipulate program execution flow through carefully crafted malicious input.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with potential access to system resources and capabilities that could be leveraged for further exploitation. Remote attackers can manipulate the BROWSER environment variable to execute arbitrary commands on the target system, potentially leading to privilege escalation, data exfiltration, or system compromise. The attack surface is particularly concerning as it can be triggered through web-based interactions, making it accessible to attackers who may not have direct system access but can influence user behavior through malicious links or content. This vulnerability demonstrates how seemingly innocuous applications can become attack vectors when proper input validation is omitted.
Mitigation strategies for CVE-2017-17523 require immediate implementation of proper input validation and sanitization measures within the lilypond-invoke-editor component. System administrators should ensure that all user-provided input is thoroughly validated and sanitized before being incorporated into command-line arguments or environment variable values. The recommended approach involves implementing strict input filtering that removes or encodes potentially dangerous characters and sequences, while also considering the use of secure coding practices that prevent direct string concatenation into system commands. Additionally, organizations should consider implementing environment variable restrictions and privilege separation to limit the potential impact of successful exploitation attempts. This vulnerability highlights the importance of following secure coding guidelines and adheres to ATT&CK technique T1059.001 for command and script injection, emphasizing the need for comprehensive input validation across all application components that interact with system-level operations.