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Advisory details: pypa / nltk/PYSEC-2026-3729
Advisory ID pypa/nltk/PYSEC-2026-3729
Aliases CVE-2026-63310
GHSA-5wp5-5229-5g6q
GHSA-gf32-cmjh-8m9v
PYSEC-2026-3729
Summary NLTK 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.
Status Published
Exploitability 0.5
Weighted Severity 5.9
Risk 3.0
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (0)
There are no known CWE.
System Score Found at
cvssv3.1 6.5 https://github.com/pypa/advisory-database/blob/main/vulns/nltk/PYSEC-2026-3729.yaml
Reference id Reference type URL
https://github.com/advisories/GHSA-5wp5-5229-5g6q
https://github.com/nltk/nltk/security/advisories/GHSA-5wp5-5229-5g6q
https://www.vulncheck.com/advisories/nltk-before-missing-post-download-integrity-verification
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N Found at https://github.com/pypa/advisory-database/blob/main/vulns/nltk/PYSEC-2026-3729.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.