CVE-2026-78682

NLTK before 3.10.3 SSRF Protection Bypass via Proxy

Published: Aug 25, 2026Updated: Aug 31, 2026 Sources: CVE List NVDCWE-918

7.5HIGH

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:HConfidentiality

High

I:NIntegrity

None

A:NAvailability

None

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Weaknesses

CWE-918

Affected Products

nltk

oss-projectaka nltk/nltk

nltkLibrary

AI / ML / ml-framework

Exploitability

Official Patch Available

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques

Command and Control

Initial Access

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References

https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh

github.com

https://www.vulncheck.com/advisories/nltk-before-ssrf-protection-bypass-via-proxy

vulncheck.com

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