Advisoriesby GlyphPath 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
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)) # ❌ VULNERABLERoot 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
pathparameter 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...
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| guarddog PyPI | < 2.7.1 | 2.7.1 |
Details and references
## 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... ## Timeline - **2026-01-05:** discovered - **2026-01-05:** Reported - **Suggested disclosure:** 30 days ## Credits **Reported by:** Charbel (dwbruijn)
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-22