# NLTK: Symlink-based arbitrary file read in IPIPANCorpusReader, bypasses nltk.pathsec entirely

Advisory record · `GHSA-3hhw-38pf-pxj6`

- **Identifiers:** `GHSA-3hhw-38pf-pxj6` · `CVE-2026-62383` · `PYSEC-2026-3726`
- **State:** Confirmed
- **Severity:** CVSS 6.8 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-22](https://cwe.mitre.org/data/definitions/22.html) · [CWE-59](https://cwe.mitre.org/data/definitions/59.html)
- **Tags:** [Path traversal](https://agentprime.io/advisories/tag/path-traversal.md)
- **Published:** 8 Sept 2026
- **Updated:** 8 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 8 Sept 2026, 16:40 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `nltk` (PyPI): affected `>=3.10.0, <3.10.2`; fixed in `3.10.2`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> NLTK versions 3.10.0 up to, but not including, 3.10.2 are affected in the IPIPANCorpusReader class. A symlink placed inside the corpus root can cause methods such as channels(), domains(), categories() and fileids(channels=...) to read arbitrary files the process can access, because the file is opened without NLTK's path security checks. An attacker needs some ability to place a symlink in the corpus directory, and no user interaction is required. Upgrade to NLTK 3.10.2 or later.

Written 5 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.8 Medium, CVSS 4.0: `CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0018, the 7th percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:38 UTC: First seen by agentprime
- 31 Oct 2026, 14:38 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-3hhw-38pf-pxj6)

## Sources

- [GitHub Advisory Database: GHSA-3hhw-38pf-pxj6](https://github.com/advisories/GHSA-3hhw-38pf-pxj6)
- [OSV: GHSA-3hhw-38pf-pxj6](https://osv.dev/vulnerability/GHSA-3hhw-38pf-pxj6)
- <https://github.com/nltk/nltk/security/advisories/GHSA-3hhw-38pf-pxj6>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-62383>
- <https://github.com/nltk/nltk/pull/3727>
- <https://github.com/nltk/nltk/commit/ee1a42e51982c4dce6ad3ee77ff1ac43894288ab>
- <https://github.com/nltk/nltk>
- <https://github.com/nltk/nltk/releases/tag/v3.10.2>
- <https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3726.yaml>
- <https://www.vulncheck.com/advisories/nltk-ipipancorpusreader-symlink-arbitrary-file-read>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-3hhw-38pf-pxj6>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-3hhw-38pf-pxj6/>. Everything for agents: <https://agentprime.io/llms.txt>.