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CVE-2026-78682 Details

Description

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:7.5 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh	CISA-ADP	ExploitVendor Advisory
https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh	[email protected]	ExploitVendor Advisory
https://www.vulncheck.com/advisories/nltk-before-ssrf-protection-bypass-via-proxy	[email protected]	Third Party Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-918	Server-Side Request Forgery (SSRF)	[email protected]

Affected Products

Product	Versions
nltk nltk	< 3.10.3
CPE cpe:2.3:a:nltk:nltk:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Aug 31, 2026	Initial Analysis	[email protected]
Aug 25, 2026	CVE Modified	CISA-ADP
Aug 25, 2026	New CVE Received	[email protected]