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Advisory record · GHSA-qx2g-xrx7-vfh8

NLTK TweetTokenizer vulnerable to denial of service through catastrophic regex backtracking

CVSS 8.7 HighEPSS 0.0074 · 55th percentile

Published by the GitHub Advisory Database at 21 Aug 2026, 00:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
nltkPyPI<3.10.13.10.1
Identifiers
GHSA-qx2g-xrx7-vfh8 · CVE-2026-72818 · PYSEC-2026-3870
Weakness (CWE)
CWE-1333
Tags
Published
21 Aug 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

NLTK versions before 3.10.1 are vulnerable to denial of service in TweetTokenizer, caused by catastrophic regular expression backtracking when tokenizing crafted input. An attacker who can submit text to a service that applies TweetTokenizer or casual_tokenize can stall that request for seconds to minutes of CPU time, with no authentication needed. Upgrade to NLTK 3.10.1 or later, which bounds the repetition in the affected pattern.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
8.7 High 4.0 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 CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0074, the 55th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:10 UTC First seen by agentprime
  2. 31 Oct 2026, 14:10 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.