Sign in Sign up
JA · EN · FR
SecPulse
Categories
CVE-2026-12261 medium CVSS 6.5

Vulnerability in nltk (CVE-2026-12261)

Summary

Vulnerability in nltk (CVE-2026-12261). Data can be tampered with by attackers. Exploitable via nltk.downloader. Mitigation: upgrade to 3.10.0 or later.

Original description

The description as published by the source.

A vulnerability in nltk.downloader in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as corpora/ and taggers/ instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.

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-2026-12261 has been found in nltk.
Attackers can target a specific entry point like nltk.downloader over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 6.5/10.
What to do: upgrade nltk to 3.10.0 or later.
If unsure, ask your IT team or search "nltk CVE-2026-12261" on the vendor's site.

CVE-2026-12261 (nltk) — CWE-284 / CVSS v3 6.5
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: nltk.downloader
Patched: 3.10.0 — 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

A vulnerability (CWE-284) exists in nltk. Attackers reach the vulnerable code path via nltk.downloader without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of nltk. Attack surface: nltk.downloader.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 3.10.0.

🛡️ 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 3.10.0

    ステージング環境で 3.10.0 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":"3.10.0"}]}]

References

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