GHSA-9rj7-rf2p-w77r CVE-2026-76218 PYSEC-2026-3840

GitPython: Unguarded git option forwarding in Repo.init enables arbitrary command execution via --template clone hooks

High PyPI

Severity: 7.7 / 10; High · CVSS 4.0
Exploit chance (EPSS): 0.72%; Chance of exploitation in the next 30 days. Higher than 53.93% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection'); CWE-94 Improper Control of Generation of Code ('Code Injection')
Fix: 3.1.58; Upgrade gitpython to this version or later

Description

Summary

Repo.init() forwards **kwargs verbatim to git init with no unsafe-option guard and no allow_unsafe_options parameter. git init --template=<dir> copies <dir>/hooks/* into the new repo's .git/hooks, so an attacker-controlled template kwarg plants a hook that executes on the next git operation → arbitrary code execution. --template is already recognized as unsafe for clone (it is on unsafe_git_clone_options, and GHSA-6p8h-3wgx-97gf covers the clone path), but Repo.init is a distinct method that never received a guard and needs an independent fix.

Root Cause

Repo.init(path, mkdir, odbt, expand_vars, **kwargs) is a bare git.init(**kwargs) (git/repo/base.py:1435) with no check_unsafe_options and no allow_unsafe_options.

Impact

Arbitrary code execution (hook fires on next git op) at the privileges of the host process. Two preconditions raise attack complexity (AC:H): the app must forward a template= kwarg (KEY control) AND the attacker must stage an executable hook directory at a known path — the same profile GHSA-6p8h-3wgx-97gf accepted as HIGH for the clone path. Default allow_unsafe_options is irrelevant here because Repo.init has no guard at all.

Proof of Concept

# attacker stages /evil/hooks/post-commit (executable)
from git import Repo
Repo.init(path, template="/evil")
# next commit runs /evil/hooks/post-commit -> ACE

Attack Chain

Entry: attacker stages /evil/hooks/post-commit (executable) and gets the app to call Repo.init(path, template='/evil').
Check: NONE on Repo.init. Bypass proof: base.py:1435 is a bare git.init(**kwargs). argv (observed): ['git','init','--template=/evil'].
Sink: git copies /evil/hooks/post-commit → <repo>/.git/hooks/post-commit.
Impact: next commit runs the hook → arbitrary code execution.

Bypass Evidence

Independently reproduced (gate harness): Repo.init(dst, template='<evil>') → argv ['git','init','--template=<evil>'] unguarded; hook copied into .git/hooks/post-commit; after git commit the INIT_ACE marker was created. --separate-git-dir=<path> is a parallel arbitrary-redirect vector through the same unguarded sink (value control only).

Affected Versions

GitPython <= 3.1.57 (unguarded git.init(**kwargs) present verbatim on the latest release tag).

Suggested Fix

Add a check_unsafe_options guard (with an allow_unsafe_options parameter) to Repo.init, consulting a denylist that includes --template and --separate-git-dir (path-taking / hook-installing options).

Reported by zx (Jace) — GitHub: @manus-use

Affected versions

PyPI

Package	Vulnerable	Fixed in
gitpython	`< 3.1.58`	`3.1.58`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

gitpython PyPI → `3.1.58`

pip

pip install --upgrade "gitpython>=3.1.58"

poetry

poetry add "gitpython>=3.1.58"

uv

uv add "gitpython>=3.1.58"

Severity breakdown

CVSS 4.0 7.7

CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack vector: Network
Attack complexity: High
Attack requirements: Present
Privileges required: Low
User interaction: None
Confidentiality (vulnerable system): High
Integrity (vulnerable system): High
Availability (vulnerable system): High
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None
Exploit maturity: Not defined
Scope: X

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack vector: Network
Attack complexity: High
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Weakness

CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

How to prevent it

Implementation: Where possible, avoid building a single string that contains the command and its arguments. Some languages or frameworks have functions that support specifying independent arguments, e.g. as an array, which is used to automatically perform the appropriate quoting or escaping while building the command. For example, in PHP, escapeshellarg() can be used to escape a single argument to system(), or exec() can be called with an array of arguments. In C, code can often be refactored from using system() - which accepts a single string - to using exec(), which requires separate function arguments for each parameter.
Architecture and Design: Understand all the potential areas where untrusted inputs can enter your product: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application. Perform input validation at well-defined interfaces.
Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
Testing: Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

CWE-94: Improper Control of Generation of Code ('Code Injection')

The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.