NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.

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History

Fri, 28 Aug 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 27 Aug 2026 16:45:00 +0000

Type Values Removed Values Added
Description NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.
Title NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader
First Time appeared Nltk
Nltk nltk
Weaknesses CWE-400
CPEs cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*
Vendors & Products Nltk
Nltk nltk
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-08-28T15:58:35.166Z

Reserved: 2026-08-27T11:15:29.420Z

Link: CVE-2026-81725

cve-icon Vulnrichment

Updated: 2026-08-27T18:24:03.206Z

cve-icon NVD

Status : Received

Published: 2026-08-27T17:21:03.247

Modified: 2026-08-28T20:20:12.380

Link: CVE-2026-81725

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-27T20:30:04Z

Weaknesses