Headline
GHSA-wfm5-v35h-vwf4: GitPython untrusted search path on Windows systems leading to arbitrary code execution
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_EXECUTABLEenvironment 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_EXECUTABLEenv var to an absolute path. - Resolve the executable manually by only looking into the
PATHenvironment 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.
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
- GHSA-wfm5-v35h-vwf4
- https://nvd.nist.gov/vuln/detail/CVE-2023-40590
- https://docs.python.org/3/library/subprocess.html#popen-constructor
Related news
GitPython is a python library used to interact with Git repositories. When resolving a program, Python/Windows look for the current working directory, and after that the PATH environment. 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`. 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. 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. There is no fix currently available for windows users, however there are a few mitigations. 1: Default to an absolute path for the git program on Windows, like `C:\\Program Files\\Git\\cmd\\git.EXE` (default git path installation). ...