CVE-2026-78682

HIGH 7.5

NLTK before 3.10.3 SSRF Protection Bypass via Proxy

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.

CWE	CWE-918
Vendor	nltk
Product	nltk
Published	Aug 25, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Affected Versions

nltk / nltk

0 < 3.10.3

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh vulncheck.com: https://www.vulncheck.com/advisories/nltk-before-ssrf-protection-bypass-via-proxy

Credits

🔍 sondt99