CVE-2026-80206

The record

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.

Affected packages

Related vulnerabilities

• CVE-2026-80205 NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability… CWE-1333
• CVE-2026-79770 Nokogiri versions before 1.19.3 contain regular expression denial of service… CWE-1333
• CVE-2026-72818 The URLS regular expression in nltk/tokenize/casual.py, compiled into… CWE-1333
• CVE-2026-59893 sqlparse is a non-validating SQL parser module for Python. CWE-1333
• CVE-2026-54284 sqlparse is a non-validating SQL parser module for Python. CWE-1333
• CVE-2026-69207 Hono is a Web application framework that provides support for any JavaScript runtime. CWE-1333
• CVE-2026-14741 HTTP::Date versions before 6.08 for Perl allow CPU exhaustion via polynomial regex… CWE-1333
• CVE-2026-49477 Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. CWE-1333