CVE-2026-126303

NLTK before 3.10.4 Denial of Service via SteppingRecursiveDescentParser.parse()

Published Nov 13, 2026 CVSS 4.0 · 8.7 High EPSS n/a KEV · Not listed
Description
NLTK before 3.10.4 contains an uncontrolled resource consumption vulnerability in SteppingRecursiveDescentParser.parse() that lacks any max_time deadline or step limit. Attackers influencing the grammar can supply an ambiguous self-embedding grammar and short token input to force unbounded top-down search, pinning CPU cores and exhausting worker pools.

Analysis

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Remediation

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Tracking

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Advisories

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History
Type Values Removed Values Added
Description NLTK before 3.10.4 contains an uncontrolled resource consumption vulnerability in SteppingRecursiveDescentParser.parse() that lacks any max_time deadline or step limit. Attackers influencing the grammar can supply an ambiguous self-embedding grammar and short token input to force unbounded top-down search, pinning CPU cores and exhausting worker pools.
Title NLTK before 3.10.4 Denial of Service via SteppingRecursiveDescentParser.parse()
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': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': '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'}

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Nov 13, 2026, 9:36 AM
Reserved
Nov 10, 2026, 8:15 PM

No data.