Vulnerability in nltk (UBUNTU-CVE-2026-33231)
Summary
Vulnerability in nltk (UBUNTU-CVE-2026-33231). Risk of unauthorized operations or information disclosure. Exploitable via GET /SHUTDOWN. Mitigation: upgrade to 2.0~b9-0ubuntu4.1~esm6 or later.
Original description
The description as published by the source.
NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. In versions 3.9.3 and prior, nltk.app.wordnet_app allows unauthenticated remote shutdown of the local WordNet Browser HTTP server when it is started in its default mode. A simple GET /SHUTDOWN%20THE%20SERVER request causes the process to terminate immediately via os._exit(0), resulting in a denial of service. Commit bbaae83db86a0f49e00f5b0db44a7254c268de9b patches the issue.
Source: OSV.dev (Open Source Vulnerabilities) OSV
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 UBUNTU-CVE-2026-33231 has been found in nltk.
Attackers can target a specific entry point like GET /SHUTDOWN over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade nltk to 2.0b9-0ubuntu4.1esm6 or later.
If unsure, ask your IT team or search "nltk UBUNTU-CVE-2026-33231" on the vendor's site.
UBUNTU-CVE-2026-33231 (nltk)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /SHUTDOWN / nltk.app.wordnet_app
Patched: 2.0~b9-0ubuntu4.1~esm6 — 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.
A vulnerability (unclassified) exists in nltk. Attackers reach the vulnerable code path via GET /SHUTDOWN without authentication.
Check the vendor advisory for the affected versions of nltk. Attack surface: GET /SHUTDOWN / nltk.app.wordnet_app.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 2.0b9-0ubuntu4.1esm6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /SHUTDOWN requests with malformed payloads or SQL meta-characters. 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
-
1Identify 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。 -
2Hunt for indicators of compromise detect
grep 'GET /SHUTDOWN' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /SHUTDOWNへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade nltk to 2.0~b9-0ubuntu4.1~esm6ステージング環境で 2.0
b9-0ubuntu4.1esm6 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と、Step 2 で見つけた異常検知の続報チェックを含めること。 -
4Post-deployment verification verify
Replay attack against GET /SHUTDOWN on staging to confirm patch closes the vector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 Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
References
- advisory ubuntu.com
- report ubuntu.com
- report cve.org
- report github.com
- report github.com