GHSA-f9j4-qggq-h239 CVE-2026-110858

GitPython Remote.pull() refspec bypasses the --upload-pack unsafe-option guard, enabling arbitrary command execution

Critical PyPI

Severity: 9.2 / 10; Critical · CVSS 4.0
Exploit chance (EPSS): 0.46%; Chance of exploitation in the next 30 days. Higher than 40.27% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'); CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
Fix: 3.2.0; Upgrade gitpython to this version or later

Description

Summary

Remote.pull() in GitPython forwards its positional refspec argument directly to the git pull child process while its unsafe-option guard inspects only keyword arguments. An application that passes attacker-influenced data as the refspec (for example a user-supplied branch or refspec parameter in a web or CI service) can supply an option-shaped value such as --upload-pack=<command>. The value bypasses the unsafe_git_pull_options check, is placed after the -- separator on the git pull command line, and is executed as the upload-pack program for local-path or SSH transports. This yields arbitrary command execution with the privileges of the calling process using the documented default arguments (allow_unsafe_options=False).

Root Cause

Remote.pull() is documented to reject dangerous options unless allow_unsafe_options=True, and --upload-pack is explicitly listed as such an option. The guard, however, only screens keyword arguments and never the positional refspec. The check builds its candidate list with Git._option_candidates([], kwargs), passing an empty list in place of the positionals, so the refspec value is never compared against unsafe_git_pull_options = ["--upload-pack"]. The normalized refspec is then forwarded verbatim to the git pull invocation. The leading -- separator that neutralizes an option-shaped refspec for git fetch and git push does not protect git pull, because git pull re-forwards its trailing positionals to an internal git fetch without re-inserting a -- separator, so the positional becomes an option to that internal fetch.

Affected function: git.remote.Remote.pull
Source: git/remote.py (guard at the check_unsafe_options call using _option_candidates([], kwargs); sink at the self.repo.git.pull("--", self, refspec, ...) invocation)

Impact

An attacker who controls the refspec value passed to Remote.pull() achieves arbitrary operating-system command execution as the process invoking GitPython, with no additional privileges and no user interaction, on the default code path. Exploitation requires that the pulled remote uses a transport that runs upload-pack on the local side, namely a local filesystem path or SSH; over HTTPS the --upload-pack value is inert because the server ignores a client-supplied upload-pack program. This transport requirement narrows the population of vulnerable deployments but does not add work for the attacker once a vulnerable target is reached. Working checkouts commonly use local-path or SSH origins, so the exposed population is substantial.

Proof of Concept

Environment: GitPython from the affected source tree; system git 2.43.0.
The pulled origin uses a local filesystem transport (protocol.file.allow=always for git >= 2.38).

Reproduction steps:

Create an origin repository reachable over a local-path transport.
In a consumer repository, register that origin and call Remote.pull() with an attacker-controlled refspec.
Observe that the injected command executes.

import git
repo = git.Repo("consumer")                 # has an origin using a local-path or ssh transport
origin = repo.remote("origin")
# Attacker-controlled refspec value; default arguments (allow_unsafe_options=False):
origin.pull(refspec="--upload-pack=touch /tmp/pwned; git-upload-pack")

cmdline: git pull -v -- origin --upload-pack=touch /tmp/pwned; git-upload-pack
[attack]  marker created (RCE)      : True
[isolate] upload_pack passed as KWARG blocked : True   (only the positional refspec escapes)
[sibling] same value via git fetch  : safe            (pull-specific behavior)
[control] benign refspec            : safe

Attack Chain

Exposure: An application calls Remote.pull(refspec=<value>) on the default path, where <value> is derived from attacker-influenced input such as a branch or refspec request parameter.
Control: The attacker supplies the string --upload-pack=<command>; git-upload-pack. The value passes through Git._unpack_args, which only flattens and stringifies it, preserving the option shape.
Path: The protocol loop calls Git.check_unsafe_protocols on the value, which only matches remote-helper transport URLs (a <transport>:: form) and does not flag an --upload-pack= token.
Guard: The unsafe-option guard calls check_unsafe_options(options=Git._option_candidates([], kwargs), ...). Because positionals are passed as an empty list, the positional refspec is never inspected against unsafe_git_pull_options.
Primitive: The value is forwarded to git pull -v -- <remote> --upload-pack=<command>; git-upload-pack; git pull re-forwards the positional to an internal git fetch without a -- separator, so it is honored as the upload-pack program.
Result: For a local-path or SSH transport, git executes <command> as the upload-pack program, giving arbitrary command execution as the calling process user.

Bypass Evidence

The relevant guard is Remote.pull()'s own check_unsafe_options call, present in the current released artifact. It is incomplete: it inspects Git._option_candidates([], kwargs), which only considers keyword arguments, so the positional refspec is never checked. This was confirmed empirically: passing the identical value as the upload_pack= keyword argument raises UnsafeOptionError, while passing it as the positional refspec does not, proving that only the positional escapes the guard.

The -- separator on the git pull command line was tested as a possible mitigation and refuted: with system git 2.43.0, git pull -- <remote> '--upload-pack=<cmd>' executed the injected command, while the identical value supplied to git fetch -- ... and git push -- ... did not execute, because those subcommands honor the -- terminator whereas git pull re-forwards positionals to an internal fetch without one. The check_unsafe_protocols transport check was also examined and does not flag the --upload-pack= token because it has no <transport>:: form. No prior published advisory for this package addresses Remote.pull, the fetch or pull refspec positional, or --upload-pack injection via a refspec; the closest accepted issue covers the same class (a positional argument escaping a keyword-only guard) in a different function and sink.

Affected Versions

Ecosystem: pip (PyPI)
Package: GitPython
Confirmed affected range: >= 3.1.30
Latest release checked: 3.1.62 (PyPI); source verified against the 3.1.62 release tag
Fix status: not fixed in any released version or on the development branch

The keyword-only pull guard together with the positional refspec sink is present in every released tag from 3.1.30 through the latest release 3.1.62, verified by inspecting the shipped git/remote.py in each tagged artifact. Version 3.1.30 introduced the unsafe_git_pull_options guard; the affected range is stated from that boundary under the incomplete-guard framing. Releases before 3.1.30 forward the refspec positionally with no unsafe-option guard and no -- separator and are also exploitable, but the range is stated conservatively from the guard-introduction boundary. No fixed release exists.

Suggested Fix

Enforce the unsafe-option invariant on the positional refspec, not only on keyword arguments. The guard should build its candidate list from the actual forwarded positionals (for example by passing the normalized refspec list into Git._option_candidates alongside kwargs) so that an option-shaped refspec such as --upload-pack=... is rejected with UnsafeOptionError unless allow_unsafe_options=True. The same correction should be verified for any other reference or refspec forwarding path that relies on the keyword-only guard. As an interim mitigation without a code change, callers should validate or reject refspec values that begin with -, avoid passing untrusted data as the refspec, and prefer HTTPS remotes where a client-supplied upload-pack program is inert.

Reported by zx (GitHub: @manus-pi).

Affected versions

PyPI

Package	Vulnerable	Fixed in
gitpython	`>= 3.1.30, < 3.2.0`	`3.2.0`

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 → `3.2.0`

pip

pip install --upgrade "gitpython>=3.2.0"

poetry

poetry add "gitpython>=3.2.0"

uv

uv add "gitpython>=3.2.0"

Severity breakdown

CVSS 4.0 9.2

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/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: Low
Attack requirements: Present
Privileges required: None
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 8.1

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

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

Weakness

CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

How to prevent it

Architecture and Design: If at all possible, use library calls rather than external processes to recreate the desired functionality.
Architecture and Design, Operation: Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
Architecture and Design: For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using the ESAPI Encoding control [REF-45] or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error.
Implementation: While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
Implementation: If the program to be executed allows arguments to be specified within an input file or from standard input, then consider using that mode to pass arguments instead of the command line.
Architecture and Design: If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. Some languages offer multiple functions that can be used to invoke commands. Where possible, identify any function that invokes a command shell using a single string, and replace it with a function that requires individual arguments. These functions typically perform appropriate quoting and filtering of arguments. For example, in C, the system() function accepts a string that contains the entire command to be executed, whereas execl(), execve(), and others require an array of strings, one for each argument. In Windows, CreateProcess() only accepts one command at a time. In Perl, if system() is provided with an array of arguments, then it will quote each of the arguments.
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. When constructing OS command strings, use stringent allowlists that limit the character set based on the expected value of the parameter in the request. This will indirectly limit the scope of an attack, but this technique is less important than proper output encoding and escaping. Note that proper output encoding, escaping, and quoting is the most effective solution for preventing OS command injection, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent OS command injection, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, when invoking a mail program, you might need to allow the subject field to contain otherwise-dangerous inputs like ";" and ">" characters, which would ne
Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Operation: Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184).
Operation: Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184).
Implementation: Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not. In the context of OS Command Injection, error information passed back to the user might reveal whether an OS command is being executed and possibly which command is being used.
Operation: Use runtime policy enforcement to create an allowlist of allowable commands, then prevent use of any command that does not appear in the allowlist. Technologies such as AppArmor are available to do this.
Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Architecture and Design, Operation: Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Operation, Implementation: When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

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.