Sign in Sign up
JA · EN · FR
SecPulse
Categories
CVE-2026-78682 high CVSS 7.5

SSRF (Server-Side Request Forgery) in nltk (CVE-2026-78682)

Summary

SSRF in nltk (CVE-2026-78682). Confidential information can be exposed externally. Exploitable via nltk.pathsec.urlopen. Mitigation: upgrade to 3.10.3 or later.

Original description

The description as published by the source.

Summary

Current NLTK source reopens SSRF in proxied environments. pathsec.urlopen() validates the requested hostname locally, but once proxy inheritance is enabled the real fetch is performed by the proxy rather than by the validated direct-connect socket path.

Details

  • Vulnerability type: Server-side request forgery
  • Affected component: nltk.pathsec.urlopen, nltk.data.load, nltk.downloader.Downloader.index, nltk.downloader.Downloader.download
  • Affected versions: Current source v3.10.0-rc2; published 3.9.4 was a negative control and did not reproduce.
  • Patched versions: Not yet patched
  • Root cause: Proxy-handler inheritance disables _SafeHTTPHandler and _SafeHTTPSHandler, so the validated hostname no longer matches the actual egress destination.

The hardened direct path pins the validated numeric destination IP before opening the socket. The proxied branch instead copies ProxyHandler instances from the global opener, marks the request as proxied, and skips the pinned handlers. I confirmed that a validated public URL can be fetched from a loopback-only internal service through the proxy path via pathsec.urlopen(), nltk.data.load(), Downloader.index(), and Downloader.download().

PoC

Preconditions

  • The runtime has an HTTP proxy configured and the caller relies on pathsec to keep network fetches SSRF-safe.

Steps

  1. Start a loopback-only HTTP server that serves secret text, a valid downloader index,…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-78682 has been found in nltk.
Attackers can target a specific entry point like nltk.pathsec.urlopen over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade nltk to 3.10.3 or later.
If unsure, ask your IT team or search "nltk CVE-2026-78682" on the vendor's site.

CVE-2026-78682 (nltk) — CWE-918 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: nltk.pathsec.urlopen / nltk.data.load / nltk.downloader.Downloader.index / nltk.downloader.Downloader.download
Patched: 3.10.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

SSRF (CWE-918) exists in nltk. Attackers reach the vulnerable code path via nltk.pathsec.urlopen without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of nltk. Attack surface: nltk.pathsec.urlopen / nltk.data.load / nltk.downloader.Downloader.index / nltk.downloader.Downloader.download.

🔥 Severity

Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 3.10.3.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'nltk' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'nltk' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で nltk を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade nltk to 3.10.3

    ステージング環境で 3.10.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip nltk
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.10.3"}]}]
PyPI nltk
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.10.3"}]}]

References

We use cookies for analytics and ad measurement. This setting applies to all Game co., Ltd. sites. Details