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.
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History
Wed, 26 Aug 2026 11:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | NLTK 3.10.2 Regular Expression Denial of Service via tgrep | |
| First Time appeared |
Nltk
Nltk nltk |
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| Weaknesses | CWE-1333 | |
| CPEs | cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Nltk
Nltk nltk |
|
| References |
| |
| Metrics |
cvssV3_1
|
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Status: PUBLISHED
Assigner: VulnCheck
Published:
Updated: 2026-08-26T12:52:23.513Z
Reserved: 2026-08-25T23:15:39.155Z
Link: CVE-2026-80206
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OpenCVE Enrichment
Updated: 2026-08-26T12:30:05Z
Weaknesses