Vulnerability Description
NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /regex/ pattern nodes and executes them via re.search against tree node labels without any validation or timeout. An attacker who controls the tgrep pattern (e.g., via tgrep_positions() or tgrep_compile() exposed to external input) can supply a pattern that triggers catastrophic backtracking, causing indefinite CPU saturation that blocks the Python process.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nltk | Nltk | < 3.10.3 |
Related Weaknesses (CWE)
References
- https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7ExploitVendor Advisory
- https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-seThird Party Advisory
- https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7ExploitVendor Advisory
FAQ
What is CVE-2026-80206?
CVE-2026-80206 is a vulnerability with a CVSS score of 5.9 (MEDIUM). NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /re...
How severe is CVE-2026-80206?
CVE-2026-80206 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-80206?
Check the references section above for vendor advisories and patch information. Affected products include: Nltk Nltk.