CVE-2014-9938 in Git
Summary
by MITRE
contrib/completion/git-prompt.sh in Git before 1.9.3 does not sanitize branch names in the PS1 variable, allowing a malicious repository to cause code execution.
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Analysis
by VulDB Data Team • 09/10/2020
The vulnerability identified as CVE-2014-9938 resides within the Git version control system's shell completion script, specifically in the contrib/completion/git-prompt.sh file. This flaw affects Git versions prior to 1.9.3 and represents a critical security issue that exploits the improper sanitization of branch names when populating the PS1 environment variable. The PS1 variable controls the command prompt displayed in interactive shell sessions, making it a prime target for malicious exploitation. When users navigate to a repository containing specially crafted branch names, the shell prompt script fails to properly escape or validate these names before incorporating them into the prompt display, creating a potential code execution vector.
The technical implementation of this vulnerability stems from the shell script's failure to properly handle special characters and escape sequences present in branch names. The git-prompt.sh script directly incorporates branch names into the PS1 variable without adequate sanitization, allowing malicious actors to embed shell commands within repository branch names. When users switch to repositories containing such malicious branch names, the shell processes the unescaped prompt string, executing arbitrary commands with the privileges of the affected user. This represents a classic command injection vulnerability that leverages the shell's interpretation of prompt strings rather than traditional input validation mechanisms. The flaw operates at the level of shell variable expansion and prompt rendering, making it particularly insidious as it can be triggered simply by changing directories into malicious repositories.
The operational impact of CVE-2014-9938 extends beyond immediate code execution capabilities to encompass broader security implications for development environments and continuous integration systems. Attackers can exploit this vulnerability to execute arbitrary commands on systems where Git shell completion is enabled, potentially leading to privilege escalation, data exfiltration, or system compromise. The vulnerability is particularly dangerous in collaborative development environments where developers frequently switch between repositories or when automated systems process repositories from untrusted sources. The attack vector requires minimal user interaction beyond normal Git operations, making it highly exploitable in real-world scenarios where developers routinely interact with various repositories. This vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and demonstrates how shell injection can occur through seemingly benign user interface elements like command prompts.
Mitigation strategies for CVE-2014-9938 primarily focus on updating Git to version 1.9.3 or later, where the sanitization issue has been addressed through proper escaping of branch names in the PS1 variable. System administrators should also consider disabling Git shell completion in high-security environments or implementing additional input validation measures. Organizations should conduct comprehensive audits of their Git configurations to identify systems with vulnerable shell completion scripts and ensure proper patch management protocols are in place. The vulnerability highlights the importance of secure coding practices in shell scripts and underscores the need for proper input sanitization even in user interface components like command prompts. Security teams should also consider implementing monitoring for unusual shell command execution patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the critical security considerations that must be applied to all components of development tools, particularly those that interact with user environments and shell contexts.