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Advisory record · GHSA-ff5c-cp5c-9wjf

NLTK: Uncontrolled resource consumption in RecursiveDescentParser via ambiguous or left-recursive grammars

CVSS 4.0, no score published

Published by the GitHub Advisory Database at 2 Sept 2026, 14:33 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
nltkPyPI<3.10.33.10.3
Identifiers
GHSA-ff5c-cp5c-9wjf · CVE-2026-12876 · PYSEC-2026-3869
Weakness (CWE)
CWE-407 · CWE-674
Tags
Published
2 Sept 2026
Updated
10 Sept 2026

Machine-written summary

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

The NLTK package versions before 3.10.3 are vulnerable to uncontrolled resource consumption in nltk.parse.RecursiveDescentParser and SteppingRecursiveDescentParser. An attacker who can supply a crafted context-free grammar, or an input, to an application that runs these parsers can cause unbounded CPU use or recursion-stack exhaustion, hanging the process (denial of service). Upgrade to NLTK 3.10.3 or later. The source gives few further details.

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
Not published None 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N GitHub Advisory Database
  • CISA KEV Not listed.
  • EPSS No score.

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.