CVE-2026-12199
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability in `nltk.app.wordnet_app` up to version 3.9.3 allows unauthenticated remote shutdown of the local WordNet Browser HTTP server when started in its default mode. The server listens on all interfaces and processes a specific unauthenticated GET request (`/SHUTDOWN%20THE%20SERVER`) to terminate the process immediately via `os._exit(0)`. This results in a denial of service, impacting service availability. The issue arises due to insufficient authentication and protection mechanisms for critical server functions.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe NLTK WordNet Browser application (nltk.app.wordnet_app) contains an unauthenticated shutdown mechanism that can be triggered via a GET request to `/SHUTDOWN%20THE%20SERVER`. When the HTTP server runs in its default configuration listening on all network interfaces, any remote attacker can immediately terminate the process using os._exit(0), causing denial of service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify if NLTK WordNet Browser is runningCheck for processes running nltk.app.wordnet_app or the NLTK wordnet server. Use commands like 'ps aux | grep wordnet' or 'netstat -anp | grep <port>' if you know the port (default is often 8080 or 8000)Affected if The NLTK WordNet Browser application is currently running as a network service
-
Determine the network binding configurationInspect how the HTTP server is started. Check the source code of wordnet_app.py for the host parameter, or use 'ss -tlnp' or 'netstat -tlnp' to see if the process binds to 0.0.0.0 (all interfaces) versus 127.0.0.1 (localhost only)Affected if The server binds to 0.0.0.0 or an external IP address rather than only 127.0.0.1
-
Verify network accessibility of the shutdown endpointFrom a remote machine or non-loopback interface, attempt a GET request to 'http://<target-ip>:<port>/SHUTDOWN%20THE%20SERVER'. If the server responds and then terminates, it is vulnerable. Alternatively, check if port is accessible externally using nmap or curlAffected if The /SHUTDOWN%20THE%20SERVER endpoint is reachable from a non-localhost source and the server terminates upon request
A defender is affected if the NLTK WordNet Browser application is running and bound to a network interface other than localhost (127.0.0.1), allowing remote unauthenticated attackers to trigger os._exit(0) and crash the service.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataRestrict the server to localhost binding (127.0.0.1) only, remove or disable the shutdown endpoint, or implement authentication for administrative functions.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-12199 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-12199 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data