CVE-2026-78682
NLTK before 3.10.3 SSRF Protection Bypass via Proxy
- State
- Published
- Severity
- 8.7 High
- Published
- Aug 25, 2026
- Updated
- Oct 8, 2026
- Reserved
- Aug 25, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | VulnCheck |
Weaknesses
- CWE-918 Server-Side Request Forgery (SSRF)
Affected Products
| Product | Versions |
|---|---|
nltknltk |
|
References
- GitHub Security Advisory (GHSA-6ww7-3frv-cqxh)vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 SSRF Protection Bypass via Proxythird-party-advisory
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