CVE-2026-76219 in GitPython
Summary
by MITRE • 08/19/2026
GitPython versions before 3.1.58 contain an arbitrary file overwrite vulnerability in IndexFile.from_tree, IndexFile.reset, and IndexFile.merge_tree methods that append caller-influenced treeish strings to git read-tree without option validation or argument separation. Attackers can inject the --index-output option to overwrite arbitrary files with a valid git-index blob, destroying existing file content at attacker-controlled writable paths.
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Analysis
by VulDB Data Team • 08/20/2026
GitPython is a Python library that provides an interface for interacting with Git repositories, allowing developers to perform version control operations programmatically within their applications. Versions prior to 3.1.58 contain a critical security flaw classified as CWE-78 Improper Neutralization of Special Elements used in an OS Command (OS Command Injection) and CWE-436 Interpretation Conflict. This vulnerability specifically affects the IndexFile class methods from_tree, reset, and merge_tree. These methods are designed to manipulate the git index file by executing underlying Git commands via subprocess calls. The core technical flaw lies in how these functions construct command-line arguments for the git read-tree utility. Instead of properly separating options from positional arguments or validating input strings against a whitelist of allowed characters, the code directly appends caller-influenced treeish strings to the argument list without sufficient sanitization.
The operational impact of this vulnerability is severe because it allows an attacker who can control the input passed to these methods to inject arbitrary command-line flags into the git process. Specifically, by injecting the --index-output option followed by a file path, an attacker can redirect the output of the index operation to overwrite any file on the system that the user running the Python script has write permissions for. This is not merely a data leak or information disclosure; it constitutes an arbitrary file overwrite vulnerability with potential consequences ranging from denial of service through destruction of critical configuration files to privilege escalation if the application runs with elevated privileges and overwrites sensitive system binaries or scripts. The attacker can effectively replace legitimate content with a valid git-index blob, which may serve as a payload for further exploitation depending on how the overwritten file is subsequently processed by other parts of the application or operating system.
This type of vulnerability aligns with MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically sub-technique related to shell commands like sh or bash, where an attacker leverages a vulnerable component to execute unintended commands. The lack of argument separation means that the git command parser interprets part of what was intended as data (the treeish string) as a control flag (--index-output). This confusion between data and code is a classic injection pattern. In environments where GitPython is used for automated deployment, CI/CD pipelines, or repository management tools, this vulnerability could be exploited remotely if the input originates from untrusted sources such as user-uploaded repositories, web forms, or API endpoints that feed into these specific IndexFile methods without proper validation layers.
Mitigation strategies must focus on immediate patching and defensive coding practices. The primary remediation is to upgrade GitPython to version 3.1.58 or later, where the developers have implemented stricter input validation and argument separation mechanisms to prevent command injection. For applications that cannot immediately update their dependencies, a temporary workaround involves implementing strict allow-lists for any inputs passed to IndexFile methods, ensuring that only alphanumeric characters, hyphens, underscores, dots, and forward slashes are permitted in treeish strings. Additionally, developers should avoid passing user-controlled data directly into subprocess calls without using safe argument handling libraries or functions that explicitly separate options from arguments. Regular security audits of codebases utilizing GitPython are recommended to identify other potential injection points where external input might influence command execution contexts.