NLTK CrubadanCorpusReader path traversal allows arbitrary file disclosure

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

2.0 · 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 · score source

EPSS

• CVE-2026-71514: 0.17% estimated exploitation activity in the next 30 days; percentile 6.55 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. loadlangngrams joins the corpus root with crubadancode, 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 langfreq, limited to paths ending in -3grams.txt whose contents parse as token count lines.

Published by the source

22 Aug 2026, 15:31 UTC

Last modified by the source

2 Sep 2026, 15:32 UTC

Source last checked

26 Oct 2026, 13:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cv22-g7mw-8v73

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# Patch Next advisory brief: CVE-2026-71514

Advisory: NLTK CrubadanCorpusReader path traversal allows arbitrary file disclosure
IDs: CVE-2026-71514, GHSA-cv22-g7mw-8v73
Record: https://patchnext.com/advisories/cve-2026-71514 (revision 1, source checked 26 Oct 2026, 13:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nltk 3.10.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nltk: affected >= 3.9.4, < 3.10.3; fixed in 3.10.3

## Suggested inspection (read-only)
- `python -m pip show nltk`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on nltk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cv22-g7mw-8v73 (GitHub-reviewed advisory GHSA-cv22-g7mw-8v73 lists affected ranges: PyPI nltk >=3.9.4 <3.10.3)

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