vulnerability / NVI-00018509 / Revision 1
pyload-ng: Incomplete Tar Path Traversal Fix in UnTar._safe_extractall via os.path.commonprefix Bypass
GitHub lists this reviewed advisory for pyload-ng. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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5.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
pyload-ng
source listed< 0.5.0b3.dev97
## Summary The `_safe_extractall()` function in `src/pyload/plugins/extractors/UnTar.py` uses `os.path.commonprefix()` for its path traversal check, which performs character-level string comparison rather than path-level comparison. This allows a specially crafted tar archive to write files outside the intended extraction directory. The correct function `os.path.commonpath()` was added to the codebase in the GHSA-7g4m-8hx2-4qh3 fix (commit 5f4f0fa) but was never applied to `_safe_extractall()`, making this an incomplete fix. ## Details The GHSA-7g4m-8hx2-4qh3 fix (commit 5f4f0fa) added a correct `is_within_directory()` function to `src/pyload/core/utils/fs.py:384-391` using `os.path.commonpath()`: ```python # fs.py:384 — CORRECT implementation def is_within_directory(base_dir, target_dir): real_base = os.path.realpath(base_dir) real_target = os.path.realpath(target_dir) return os.path.commonpath([real_base, real_target]) == real_base ``` However, the `_safe_extractall()` function in `UnTar.py:10-22` was left unchanged with the broken `os.path.commonprefix()`: ```python # UnTar.py:10-22 — VULNERABLE implementation def _safe_extractall(tar, path=".", members=None, *
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-mvwx-582f-56r7 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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