Vulnerability Details 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 15.6%
CVSS Severity
CVSS v3 Score 7.5
Products affected by CVE-2026-78682
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cpe:2.3:a:nltk:nltk:2.0.1
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cpe:2.3:a:nltk:nltk:2.0.3
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cpe:2.3:a:nltk:nltk:2.0.4
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cpe:2.3:a:nltk:nltk:3.0.0
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cpe:2.3:a:nltk:nltk:3.0.1
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cpe:2.3:a:nltk:nltk:3.0.2
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cpe:2.3:a:nltk:nltk:3.0.3
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cpe:2.3:a:nltk:nltk:3.0.4
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cpe:2.3:a:nltk:nltk:3.0.5
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cpe:2.3:a:nltk:nltk:3.10.0
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cpe:2.3:a:nltk:nltk:3.10.1
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cpe:2.3:a:nltk:nltk:3.10.2
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cpe:2.3:a:nltk:nltk:3.2.1
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cpe:2.3:a:nltk:nltk:3.2.2
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cpe:2.3:a:nltk:nltk:3.2.3
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cpe:2.3:a:nltk:nltk:3.2.4
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cpe:2.3:a:nltk:nltk:3.2.5
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cpe:2.3:a:nltk:nltk:3.4.1
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cpe:2.3:a:nltk:nltk:3.4.3
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cpe:2.3:a:nltk:nltk:3.4.4
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cpe:2.3:a:nltk:nltk:3.4.5
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cpe:2.3:a:nltk:nltk:3.6.1
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cpe:2.3:a:nltk:nltk:3.6.2
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cpe:2.3:a:nltk:nltk:3.6.3
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cpe:2.3:a:nltk:nltk:3.6.4
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cpe:2.3:a:nltk:nltk:3.6.5
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cpe:2.3:a:nltk:nltk:3.6.6
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cpe:2.3:a:nltk:nltk:3.6.7
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cpe:2.3:a:nltk:nltk:3.8.1
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cpe:2.3:a:nltk:nltk:3.9.1
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cpe:2.3:a:nltk:nltk:3.9.2
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cpe:2.3:a:nltk:nltk:3.9.3
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cpe:2.3:a:nltk:nltk:3.9.4