CVE-2026-80206
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.
How to fix
- nltk nltk3.10.3 or later
- nltk3.10.3 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| nltk nltk | v < 3.10.3 | 3.10.3 |
| nltkPyPI | v < 3.10.3 | 3.10.3 |
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Attack Surface Management
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