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VULNERABILITIES

CVE-2026-80206 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:5.9 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7 CISA-ADPExploitVendor Advisory
https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7 [email protected]ExploitVendor Advisory
https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-service-via-tgrep [email protected]Third Party Advisory

Weakness Enumeration

CWE-IDCWE NameSource
CWE-1333Inefficient Regular Expression Complexity[email protected]

Affected Products

ProductVersions
nltk nltk
< 3.10.3

CPE

  • cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*

Remediation

  • No remediation found in references.

Change History

3 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-80206
NVD Published Date:
Aug 26, 2026
NVD Last Modified:
Sep 1, 2026
Source:
[email protected]
CVE-2026-80206 Details - Not Deferred