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NLTK before 3.10.3 SSRF Protection Bypass via Proxy

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-78682

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-78682

nltk

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "vendor": "nltk",
    "product": "nltk",
    "versions": [
      {
        "status": "affected",
        "version": "0",
        "lessThan": "3.10.3",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "3.10.3",
        "versionType": "semver"
      }
    ],
    "packageURL": "pkg:pypi/nltk",
    "defaultStatus": "unaffected"
  }
]
Related CVEs
CVE-2026-78682

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#12891 · Revision 1
Added to Heist Feed
Publisher date
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