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CVE-2026-81726 high CVSS 7.0

Path Traversal in nltk (CVE-2026-81726)

Summary

Path traversal in nltk (CVE-2026-81726). Confidential information can be exposed externally. Exploitable via TransitionParser.train.

Original description

The description as published by the source.

NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs when pathsec is enabled.

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-2026-81726 has been found in nltk.
Attackers can target a specific entry point like TransitionParser.train over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.0/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "nltk CVE-2026-81726" on the vendor's site.

CVE-2026-81726 (nltk) — CWE-22 / CVSS v3 7.0
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: TransitionParser.train / TransitionParser.parse / AveragedPerceptron.save / AveragedPerceptron.load
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

Path traversal (CWE-22) exists in nltk. Attackers reach the vulnerable code path via TransitionParser.train without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of nltk. Attack surface: TransitionParser.train / TransitionParser.parse / AveragedPerceptron.save / AveragedPerceptron.load.

🔥 Severity

Severity: High (CVSS 7.0/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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
    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"}]}]
PyPI nltk
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"3.10.3"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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