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.
- Affected products
- Nltk
- Fix
- Available
- CVSS 4.0
- 8.7 HIGH
- CVSS 3.1
- 7.5 HIGH
- EPSS
- 0.2% (16th percentile)
- Weakness
- CWE-918
- NVD status
- Received
- Published
- 2026-08-25
No indexed exploits for CVE-2026-78682 yet
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