Security Flaw in NLTK Prior to Version 3.9.3
CVE-2026-63310

9.3CRITICAL

Key Information:

Vendor

Nltk

Status
Nltk
Vendor
CVE Published:
22 August 2026

What is CVE-2026-63310?

NLTK versions before 3.9.3 are vulnerable due to a failure to verify the integrity of files post-download. This shortcoming allows attackers to exploit man-in-the-middle scenarios or DNS poisoning attacks, injecting malicious content into packages that are then extracted without proper validation. Users of NLTK are urged to upgrade to the latest version to mitigate this risk.

Affected Version(s)

nltk 0 < 3.9.3

nltk 3.9.3

References

https://github.com/nltk/nltk/security/advisories/GHSA-5wp...
vendor-advisory
https://www.vulncheck.com/advisories/nltk-before-missing-...
third-party-advisory

CVSS V4

Score:
9.3
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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