CVE-2026-126297

NLTK before 3.10.4 CPU Denial of Service via ConllCorpusReader srl_instances

Published Nov 13, 2026 CVSS 4.0 · 8.7 High EPSS n/a KEV · Not listed

Description

NLTK before 3.10.4 contains a quadratic-time denial of service vulnerability in ConllCorpusReader._get_srl_instances that allows remote attackers to exhaust CPU through nested span rescans. Attackers can supply a crafted CoNLL SRL corpus with many predicates and span columns, placing the head span last, to pin a core for minutes.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

nltk

unaffected

Version	Status	Constraints
`0`	affected	< 3.10.4
`3.10.4`	unaffected	—

No data.

No data available yet.

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

No advisories available

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://github.com/nltk/nltk/security/advisories/GHSA-v8f3-6phw-6mh9
https://www.vulncheck.com/advisories/nltk-before-3.10.4-cpu-denial-of-service-via-conllcorpusreader-srl-instances

History

Nov 13, 2026 9:45 AM Description updated. Title updated. First appearance in the feed. Weaknesses updated. Affected versions updated. Affected vendors updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		NLTK before 3.10.4 contains a quadratic-time denial of service vulnerability in ConllCorpusReader._get_srl_instances that allows remote attackers to exhaust CPU through nested span rescans. Attackers can supply a crafted CoNLL SRL corpus with many predicates and span columns, placing the head span last, to pin a core for minutes.
Title		NLTK before 3.10.4 CPU Denial of Service via ConllCorpusReader srl_instances
First Time appeared		Nltk Nltk nltk
Weaknesses		CWE-400
CPEs		cpe:2.3:a:nltk:nltk::::::::
Vendors & Products		Nltk Nltk nltk
References		https://github.com/nltk/nltk/security/advisories/GHSA-v8f3-6phw-6mh9 https://www.vulncheck.com/advisories/nltk-before-3.10.4-cpu-denial-of-service-via-conllcorpusreader-srl-instances
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'}`