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GitPython untrusted search path on Windows systems leading to arbitrary code execution

High severity GitHub Reviewed Published Aug 26, 2023 in gitpython-developers/GitPython • Updated Sep 20, 2024

Package

pip gitpython (pip)

Affected versions

<= 3.1.32

Patched versions

3.1.33

Description

Summary

When resolving a program, Python/Windows look for the current working directory, and after that the PATH environment (see big warning in https://docs.python.org/3/library/subprocess.html#popen-constructor). GitPython defaults to use the git command, if a user runs GitPython from a repo has a git.exe or git executable, that program will be run instead of the one in the user's PATH.

Details

This is more of a problem on how Python interacts with Windows systems, Linux and any other OS aren't affected by this. But probably people using GitPython usually run it from the CWD of a repo.

The execution of the git command happens in

https://github.com/gitpython-developers/GitPython/blob/1c8310d7cae144f74a671cbe17e51f63a830adbf/git/cmd.py#L277

https://github.com/gitpython-developers/GitPython/blob/1c8310d7cae144f74a671cbe17e51f63a830adbf/git/cmd.py#L983-L996

And there are other commands executed that should probably be aware of this problem.

PoC

On a Windows system, create a git.exe or git executable in any directory, and import or run GitPython from that directory

python -c "import git"

The git executable from the current directory will be run.

Impact

An attacker can trick a user to download a repository with a malicious git executable, if the user runs/imports GitPython from that directory, it allows the attacker to run any arbitrary commands.

Possible solutions

  • Default to an absolute path for the git program on Windows, like C:\\Program Files\\Git\\cmd\\git.EXE (default git path installation).
  • Require users to set the GIT_PYTHON_GIT_EXECUTABLE environment variable on Windows systems.
  • Make this problem prominent in the documentation and advise users to never run GitPython from an untrusted repo, or set the GIT_PYTHON_GIT_EXECUTABLE env var to an absolute path.
  • Resolve the executable manually by only looking into the PATH environment variable (suggested by @Byron)

Note

This vulnerability was reported via email, and it was decided to publish it here and make it public, so the community is aware of it, and a fix can be provided.

References

@Byron Byron published to gitpython-developers/GitPython Aug 26, 2023
Published by the National Vulnerability Database Aug 28, 2023
Published to the GitHub Advisory Database Aug 29, 2023
Reviewed Aug 29, 2023
Last updated Sep 20, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction Active
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

0.053%
(23rd percentile)

Weaknesses

CVE ID

CVE-2023-40590

GHSA ID

GHSA-wfm5-v35h-vwf4

Source code

Credits

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