NLTK before 3.9.3 Missing Post-Download Integrity Verification

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63310
StatePUBLISHED
AssignerVulnCheck
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 15:16:19 UTC
Updated2026-08-24 20:16:55 UTC
DescriptionNLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.

Risk And Classification

Primary CVSS: v4.0 9.3 CRITICAL from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.001540000 probability, percentile 0.050660000 (date 2026-08-23)

Problem Types: CWE-494 | CWE-494 Download of Code Without Integrity Check

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary9.3CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS9.3CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
3.1[email protected]Secondary7.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:H
3.1CNACVSS7.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:H

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
High
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nltk Nltk affected 3.9.3 semver Not specified
CNA Nltk Nltk unaffected 3.9.3 semver Not specified

References

ReferenceSourceLinkTags
github.com/nltk/nltk/security/advisories/GHSA-5wp5-5229-5g6q [email protected] github.com
www.vulncheck.com/advisories/nltk-before-missing-post-download-integrity-verifi... [email protected] www.vulncheck.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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