vulnerability / NVI-00016457 / Revision 1
NLTK: FileSystemPathPointer.open() sandbox check is dead code — arbitrary file read via file:// protocol
GitHub lists this reviewed advisory for nltk. 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
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.5 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.
nltk
source listed<= 3.9.3
### Summary There's a logic bug in `FileSystemPathPointer.open()` inside `nltk/data.py` that makes the sandbox check permanently inert. The guard condition is always `False` — meaning any file the process can read is accessible by passing a `file://` URL to `nltk.data.load()`. --- ### Details In `nltk/data.py`, `FileSystemPathPointer.open()` was patched at some point with a comment saying "SECURITY PATCH ENFORCING SANDBOX", but the check doesn't work: ```python def open(self, encoding=None): path = os.path.normpath(self._path) # Block raw absolute reads such as "/" "C:\\Windows" etc. if os.path.isabs(path) and path != os.path.normpath(self._path): raise ValueError(f"Direct absolute file access blocked: {path}") stream = open(self._path, "rb") ``` `path` is set to `os.path.normpath(self._path)` on line 1, then compared against `os.path.normpath(self._path)` again in the condition. They are always equal. The `ValueError` never fires. On top of that, `__init__` already calls `os.path.abspath()` before storing `self._path`, so it's normalized before `open()` is even called. Running `normpath` on it again changes nothing. The `stream = open(self._path, "
03 / Response
What to do next
- investigate
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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-72r2-7mfr-5xr9 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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