NLTK before 3.9.3 Missing Post-Download Integrity Verification
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.
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-12259US | medium6.5OT elevated | — | ||
In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract them before enforcing SHA-256 or MD5 ch… | ||||
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references
External citations — patches, advisories, analysis.
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63310.jsonADVISORY
- https://github.com/nltk/nltk/security/advisories/GHSA-5wp5-5229-5g6qADVISORY
- https://nvd.nist.gov/vuln/detail/CVE-2026-63310ADVISORY
- https://www.vulncheck.com/advisories/nltk-before-missing-post-download-integrity-verificationADVISORY
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