CVE-2026-80206
8.2
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Summary
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 Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| nltk | nltk | 0 < 3.10.3 | affected |
| nltk | nltk | 3.10.3 | unaffected |
Weaknesses
- CWE-1333: Inefficient Regular Expression Complexity
ADP Enrichment
CISA ADP Vulnrichment
- SSVC:
- Exploitation: poc
- Automatable: no
- Technical Impact: partial
Additional References
References
- https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7
- https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-service-via-tgrep
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