Unauthenticated remote shutdown in nltk.app.wordnet_app

Exploitation

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

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-33231: 1.24% estimated exploitation activity in the next 30 days; percentile 69.12 (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.

Summary nltk.app.wordnetapp allows unauthenticated remote shutdown of the local WordNet Browser HTTP server when it is started in its default mode. A simple GET /SHUTDOWN%20THE%20SERVER request causes the process to terminate immediately via os.exit(0), resulting in a denial of service. Details The vulnerable logic is in nltk/app/wordnetapp.py: - nltk/app/wordnetapp.py:242 - The server listens on all interfaces: - server = HTTPServer(("", port), MyServerHandler) - nltk/app/wordnetapp.py:87 - Incoming requests are checked for the exact path: - if unquoteplus(sp) == "SHUTDOWN THE SERVER": - nltk/app/wordnetapp.py:88 - The shutdown protection only depends on servermode - nltk/app/wordnetapp.py:93 - In the default mode (runBrowser=True, therefore servermode=False), the handler terminates the process directly: - os.exit(0) This means any party that can reach the listening port can stop the service with a single unauthenticated GET request when the browser is started in its normal mode.…

Published by the source

19 Mar 2026, 12:42 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-jm6w-m3j8-898g

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-jm6w-m3j8-898g

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# Patch Next advisory brief: CVE-2026-33231

Advisory: Unauthenticated remote shutdown in nltk.app.wordnet_app
IDs: CVE-2026-33231, GHSA-jm6w-m3j8-898g
Record: https://patchnext.com/advisories/cve-2026-33231 (revision 2, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nltk 3.9.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nltk: affected <= 3.9.3; fixed in 3.9.4

## 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://osv.dev/vulnerability/GHSA-jm6w-m3j8-898g (OSV record GHSA-jm6w-m3j8-898g lists affected ranges: PyPI nltk >=0 <3.9.4 (fixed))
- Verified: https://github.com/advisories/GHSA-jm6w-m3j8-898g (GitHub-reviewed advisory GHSA-jm6w-m3j8-898g lists affected ranges: PyPI nltk >=0 <=3.9.3)

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