CVE-2017-14867 in Git
Summary
by MITRE
Git before 2.10.5, 2.11.x before 2.11.4, 2.12.x before 2.12.5, 2.13.x before 2.13.6, and 2.14.x before 2.14.2 uses unsafe Perl scripts to support subcommands such as cvsserver, which allows attackers to execute arbitrary OS commands via shell metacharacters in a module name. The vulnerable code is reachable via git-shell even without CVS support.
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Analysis
by VulDB Data Team • 01/14/2021
The vulnerability identified as CVE-2017-14867 represents a critical command injection flaw within the Git version control system that affects multiple release branches including 2.10.x through 2.14.x. This security weakness stems from the improper handling of user-supplied input within Git's Perl scripts that support certain subcommands, particularly cvsserver which enables CVS protocol access. The vulnerability exists because Git's implementation of these scripts fails to properly sanitize or escape input parameters before incorporating them into shell commands, creating an avenue for malicious actors to inject arbitrary operating system commands through carefully crafted module names.
The technical flaw manifests when Git processes module names through Perl scripts that directly execute shell commands without adequate input validation or sanitization. Attackers can exploit this by providing module names containing shell metacharacters such as semicolons, ampersands, or backticks that get interpreted by the underlying shell during command execution. This unsafe practice violates fundamental security principles outlined in CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and CWE-94, which covers improper control of generation of code. The vulnerability is particularly dangerous because it can be triggered through git-shell, which means attackers do not need to have explicit CVS support enabled to exploit the flaw, making the attack surface significantly larger.
The operational impact of this vulnerability extends beyond simple command injection to potentially allow full system compromise when attackers can leverage the affected Git installations. Since Git is widely used across development environments, CI/CD pipelines, and source code repositories, an attacker who gains access to a vulnerable Git server can execute arbitrary commands with the privileges of the Git user account. This could lead to data exfiltration, system compromise, or the establishment of persistent backdoors within development infrastructure. The vulnerability's reach is amplified by the fact that git-shell is commonly used for secure remote access to Git repositories, making it a prime target for attackers seeking to exploit repository access points. According to ATT&CK framework category T1059.001, this vulnerability enables an attacker to execute commands through the command and scripting interpreter, while T1068 covers the exploitation of vulnerabilities to gain system-level privileges.
Mitigation strategies for CVE-2017-14867 require immediate patching of all affected Git installations to versions 2.10.5, 2.11.4, 2.12.5, 2.13.6, or 2.14.2 respectively, which contain the necessary fixes to properly sanitize input parameters before shell command execution. Organizations should also implement network segmentation and access controls to limit exposure of Git servers to untrusted networks, while monitoring for suspicious activity patterns that might indicate exploitation attempts. Additionally, administrators should consider disabling unnecessary Git subcommands that rely on Perl scripts, particularly cvsserver, when they are not actively required for operations. The remediation process should include thorough testing of patched environments to ensure that legitimate Git functionality remains intact while the vulnerability is eliminated. Regular security assessments of Git installations and continuous monitoring of security advisories are essential to prevent similar vulnerabilities from being exploited in the future, as this flaw demonstrates the critical importance of proper input validation and sanitization in system components that interface with operating system commands.