GuardDog Path Traversal Vulnerability Leads to Arbitrary File Overwrite and RCE
Summary
A path traversal vulnerability exists in GuardDog's safe_extract() function that allows malicious PyPI packages to write arbitrary files outside the intended extraction directory, leading to Arbitrary File Overwrite and Remote Code Execution on systems running GuardDog.
CWE: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)
Details
Vulnerable Code
File: guarddog/utils/archives.py
```python
elif zipfile.is_zipfile(source_archive):
with zipfile.ZipFile(source_archive, "r") as zip:
for file in zip.namelist():
# Note: zip.extract cleans up any malicious file name
# such as directory traversal attempts This is not the
# case of zipfile.extractall
zip.extract(file, path=os.path.join(target_directory, file)) # ❌ VULNERABLE
```
Root Cause
The comment about zip.extract() fooled me at first :) then I noticed the os.path.join() call.
The vulnerability stems from incorrect usage of Python's zipfile.ZipFile.extract() API:
- The
path parameter should be the target directory, not a full file path extract() automatically appends the member name to the path- By passing
os.path.join(target_directory, file), GuardDog causes the filename to be appended twice - This breaks zipfile's built-in path traversal sanitization
Attack Vector
1. Attacker creates malicious wheel with path traversal filenames
2. Uploads to PyPI or distributes directly
3. Package scan: guarddog pypi scan malicious-pkg
4. GuardDog downloads and extracts the package
5. Malicious files written to arbitrary locations
6. Code execution could be achieved
Impact
Impact depends on how GuardDog is running and under which environment.
Critical Scenarios
1. Immediate Code Execution
- Write to
~/.bashrc → executes on next shell - Write to
~/.profile → executes on login
2. Persistent Backdoors
- Write to
~/.ssh/authorized_keys → SSH access - Write to
/etc/cron.d/malicious → scheduled execution (if root) - Write to systemd user services → persistent execution
and more...
Credits
Reported by: Charbel (dwbruijn)
