Vulnerability Description
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nltk | Nltk | < 3.10.0 |
Related Weaknesses (CWE)
References
- https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2ExploitVendor Advisory
- https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafThird Party Advisory
- https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2ExploitVendor Advisory
FAQ
What is CVE-2026-78683?
CVE-2026-78683 is a vulnerability with a CVSS score of 9.6 (CRITICAL). NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_...
How severe is CVE-2026-78683?
CVE-2026-78683 has been rated CRITICAL with a CVSS base score of 9.6/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-78683?
Check the references section above for vendor advisories and patch information. Affected products include: Nltk Nltk.