CVE-2026-78682

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh	Exploit Vendor Advisory
https://www.vulncheck.com/advisories/nltk-before-ssrf-protection-bypass-via-proxy	Third Party Advisory
https://github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxh	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-08-25 02:16

Updated : 2026-08-31 19:05

NVD link : CVE-2026-78682

Mitre link : CVE-2026-78682

CVE.ORG link : CVE-2026-78682

JSON object : View

Products Affected

nltk

nltk

CWE

CWE-918

Server-Side Request Forgery (SSRF)

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