CVE-2026-81726: NLTK through 3.10.3 Path Traversal via Model-Artifact APIs
NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs when pathsec is enabled.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
NLTKto a version that resolves this vulnerability.Fixed in 3.10.3 - Configuration
Disable pathsec or otherwise prevent use of the model-artifact APIs pathsec-bypass behavior by ensuring model-artifact raw file operations cannot be performed on caller-controlled paths.
NLTK model-artifact APIs pathsec = enabled
Event History
Frequently Asked Questions
Which applications are realistically exposed to this issue?
Applications using NLTK through 3.10.3 are exposed when they enable pathsec and pass attacker-controlled paths to the affected model-artifact APIs: TransitionParser, AveragedPerceptron, PerceptronTagger, or maxent parameter APIs.
What does an attacker need to exploit the vulnerability?
An attacker needs a way to influence a file path supplied to one of the affected APIs. No privileges or user interaction are required according to the provided vector, but exploitation has high attack complexity.
Does enabling pathsec protect affected applications?
No. The issue specifically bypasses pathsec enforcement because the affected APIs use raw file operations on caller-controlled paths, allowing reads or writes outside configured sandbox roots.
How can I determine whether my application is affected?
Review whether it uses NLTK through 3.10.3, has pathsec enabled, and invokes the listed model-artifact APIs with paths derived from untrusted input. Such paths may permit access outside the intended sandbox root.