Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-78682

CVE-2026-78682HIGH

NLTK before 3.10.3 SSRF Protection Bypass via Proxy

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   H   N   N    8.7   .0043   35.5     —

AFFECTED
  Product  Versions     Fixed
  nltk     unspecified  3.10.3

TIMELINE
  Aug 25  Reserved by VulnCheck
  Aug 25  Published (CNA: VulnCheck)
  Aug 31  EXPLOIT PUBLISHED — CVE-2026-78682 (nltk). Public exploit reference added.

CWE-918 · CNA: VulnCheck · CVSS v4.0 · 2 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 25, 2026	Reserved	Reserved by VulnCheck
August 25, 2026	Published	Published (CNA: VulnCheck)
August 31, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-78682 (nltk). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
nltk	nltk	—	—	3.10.3

Weaknesses

CWE-918

References (2)

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]

Authoritative record: CVE-2026-78682 at cve.org

Vendors: nltk

Weaknesses: CWE-918

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-78682 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.