CVE-2026-78682
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
nltkPyPI | < 3.10.3 | 3.10.3 |
Affected products
2Patches
Vulnerability mechanics
References
7- github.com/nltk/nltk/security/advisories/GHSA-6ww7-3frv-cqxhnvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-6ww7-3frv-cqxhghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-78682ghsaADVISORY
- www.vulncheck.com/advisories/nltk-before-ssrf-protection-bypass-via-proxynvdThird Party AdvisoryWEB
- github.com/nltk/nltk/commit/767333a005a1cd3d82d2029215f2dbe66a5844d9ghsaWEB
- github.com/nltk/nltk/releases/tag/v3.10.3ghsaWEB
- github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3733.yamlghsaWEB
News mentions
2- Nltk Library: 16 Vulnerabilities Including Critical RCE Disclosed in BatchVypr Intelligence · Aug 27, 2026
- Nltk Library: Critical RCE and High-Severity Flaws Disclosed TogetherVypr Intelligence · Aug 25, 2026