High [CVE-2026-81725] Regular Expression Denial of Service via malformed TEI blocks
This high-severity Red Hat Linux advisory covers CVE-2026-81725 affecting Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed.
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Summary
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. A flaw was found in NLTK, specifically within the Pl196xCorpusReader component.
A remote attacker can exploit this by supplying malformed Text Encoding Initiative (TEI) blocks containing numerous unmatched opening tags. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-1333. Affected Red Hat products: Exploit Intelligence; Lightspeed Core; OpenShift Lightspeed; Red Hat Ansible Automation Platform 2; Red Hat OpenShift AI (RHOAI).
Red Hat does not currently list a fixing RHSA for this CVE.
- < 3.10.3
Official advisory · high-confidence parse· fetched 57 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 57 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · high-confidence parse· fetched 57 minutes ago·verify at source
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