CVE-2026-80205

NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex

State: Published
Severity: 8.7 High
Published: Aug 26, 2026
Updated: Sep 1, 2026
Reserved: Aug 25, 2026

Description

NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that accept user-supplied regular expressions without validation or timeout. Attackers can supply crafted regex patterns that cause catastrophic backtracking, resulting in indefinite CPU saturation and denial of service to all users of the Python process.

Scores

CVSS	Score	Vector	Source
4.0	8.7 High	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N	VulnCheck
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	VulnCheck

Weaknesses

CWE-1333 Inefficient Regular Expression Complexity

Affected Products

Product	Versions
nltknltk	before 3.10.0Affected 3.10.0Not affected

References

GitHub Security Advisory (GHSA-rrv8-h7p8-rx55)vendor-advisory
VulnCheck Advisory: NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regexthird-party-advisory
http://www.openwall.com/lists/oss-security/2026/09/01/3

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.