CVE-2018-17456 in Git
Summary
by MITRE
Git before 2.14.5, 2.15.x before 2.15.3, 2.16.x before 2.16.5, 2.17.x before 2.17.2, 2.18.x before 2.18.1, and 2.19.x before 2.19.1 allows remote code execution during processing of a recursive "git clone" of a superproject if a .gitmodules file has a URL field beginning with a '-' character.
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Analysis
by VulDB Data Team • 06/21/2024
The vulnerability identified as CVE-2018-17456 represents a critical remote code execution flaw in Git versions prior to specific patch releases. This vulnerability manifests during the processing of recursive git clone operations when a superproject contains a .gitmodules file with a URL field beginning with a '-' character. The issue stems from Git's improper handling of command-line arguments when parsing module URLs, creating a dangerous condition where malicious input can be interpreted as command-line options rather than simple URL strings. This fundamental flaw in argument parsing and validation creates an attack surface where remote adversaries can potentially execute arbitrary code on systems performing affected git clone operations. The vulnerability is particularly concerning because it leverages the common practice of recursive cloning in software development workflows where developers often work with superprojects that reference multiple submodules through .gitmodules configuration files.
The technical implementation of this vulnerability aligns with CWE-15 (External Control of System or Configuration Setting) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command) as the flaw occurs when Git interprets user-supplied input from the .gitmodules file as command-line arguments rather than as simple URL parameters. When Git encounters a URL field starting with a '-' character in the .gitmodules file, it treats this as the beginning of a command-line option, potentially allowing attackers to inject malicious commands that get executed during the cloning process. This behavior violates the principle of proper input validation and sanitization, as the system fails to properly distinguish between legitimate command-line options and user-supplied data that should be treated as literal strings. The attack vector requires a remote attacker to control or influence the content of a .gitmodules file within a repository that will be cloned recursively, making it particularly dangerous in collaborative environments where multiple parties contribute to project configurations.
The operational impact of CVE-2018-17456 extends beyond simple code execution capabilities to encompass potential system compromise and data integrity violations. When a developer performs a recursive git clone operation on an affected system, the vulnerability can be triggered through a specially crafted .gitmodules file that contains malicious command injection payloads. This vulnerability affects not just individual developers but entire organizations that rely on Git for version control and collaboration, as it can be exploited through supply chain attacks where compromised repositories contain malicious module configurations. The exploitation scenario typically involves a victim cloning a repository that references a submodule with a malicious URL starting with a dash character, leading to arbitrary command execution with the privileges of the user performing the clone operation. This vulnerability can potentially lead to complete system compromise, data exfiltration, and persistent backdoor installation, making it a critical concern for security-conscious organizations. The impact is further amplified by the widespread adoption of Git across development environments and the common practice of using recursive cloning for complex projects.
Mitigation strategies for CVE-2018-17456 focus on immediate version upgrades and operational security measures to prevent exploitation. Organizations should immediately upgrade to Git versions 2.14.5, 2.15.3, 2.16.5, 2.17.2, 2.18.1, or 2.19.1 respectively, which contain the necessary patches to address the command-line argument parsing vulnerability. Additionally, organizations should implement strict validation of .gitmodules files in their repositories, particularly in environments where multiple parties contribute to project configurations. Security controls should include automated scanning of repository configurations for potentially malicious URL patterns and implementing network segmentation to limit exposure of systems that perform recursive cloning operations. The vulnerability also highlights the importance of input validation practices and adherence to secure coding principles, as demonstrated by the ATT&CK technique T1059.001 (Command and Scripting Interpreter) which covers the execution of malicious commands through argument injection. Regular security awareness training for development teams on the risks of untrusted repository content and proper handling of submodule configurations is also recommended to reduce the likelihood of successful exploitation through social engineering or supply chain attacks.