CVE-2015-8968 in git-fastclone
Summary
by MITRE
git-fastclone before 1.0.1 permits arbitrary shell command execution from .gitmodules. If an attacker can instruct a user to run a recursive clone from a repository they control, they can get a client to run an arbitrary shell command. Alternately, if an attacker can MITM an unencrypted git clone, they could exploit this. The ext command will be run if the repository is recursively cloned or if submodules are updated. This attack works when cloning both local and remote repositories.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2015-8968 represents a critical security flaw in git-fastclone versions prior to 1.0.1 that enables arbitrary shell command execution through malicious manipulation of .gitmodules configuration files. This vulnerability operates at the intersection of software supply chain security and command injection risks, where an attacker can exploit the recursive cloning behavior of git to execute unintended shell commands on the victim's system. The flaw specifically targets the handling of external commands during submodule operations, creating a dangerous attack vector that can be leveraged through multiple exploitation pathways. The vulnerability is categorized under CWE-78 as a failure to properly sanitize command arguments, making it a classic command injection vulnerability that can be exploited in various operational contexts.
The technical mechanism behind this vulnerability involves the improper execution of shell commands when git-fastclone processes submodule configurations. When a repository with malicious .gitmodules entries is cloned recursively, the system executes external commands specified in these configuration files without adequate input validation or sanitization. This occurs during both local and remote repository cloning operations, making the attack surface particularly broad as it affects all scenarios where recursive cloning takes place. The vulnerability manifests when the ext command parameter is processed during submodule updates or recursive clones, allowing attackers to inject arbitrary shell commands that get executed with the privileges of the user performing the clone operation. This behavior aligns with ATT&CK technique T1059.001 for command and script injection, demonstrating how seemingly benign configuration files can become attack vectors for privilege escalation and remote code execution.
The operational impact of CVE-2015-8968 extends beyond simple command execution to encompass potential privilege escalation and persistent access exploitation. Attackers can leverage this vulnerability to execute malicious commands that may include data exfiltration, system reconnaissance, or installation of additional malware on the victim's system. The vulnerability is particularly dangerous in environments where users frequently clone repositories from untrusted sources or when network traffic is not properly secured, as it can be exploited through man-in-the-middle attacks against unencrypted git clone operations. The attack can be executed by an attacker who controls a repository that users will clone recursively, or by intercepting network traffic to modify the .gitmodules content during transmission. This makes the vulnerability exploitable in both direct and indirect attack scenarios, increasing its overall threat potential and making it a significant concern for organizations relying on git-based workflows and collaborative development practices.
Mitigation strategies for CVE-2015-8968 require both immediate patching and operational security improvements. The most effective immediate solution involves upgrading to git-fastclone version 1.0.1 or later, which addresses the command injection vulnerability through proper input validation and sanitization of external command parameters. Organizations should also implement network security measures including encrypted git operations, proper network segmentation, and monitoring for suspicious cloning activities. Additional defensive measures include restricting recursive clone operations in high-security environments, implementing strict repository access controls, and conducting regular security audits of .gitmodules configurations. The vulnerability highlights the importance of input validation in all software components that handle external data, particularly in tools that interact with version control systems where users may be exposed to untrusted repository content. Security teams should also consider implementing automated scanning tools that can detect potentially malicious .gitmodules entries and establish security awareness training to educate users about the risks of cloning repositories from untrusted sources.