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Public proof of conceptFix available

CVE-2026-33231

A public proof of concept exists; no exploitation attested.

  • Published2026-03-20
  • WeaknessCWE-306

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. In versions 3.9.3 and prior, `nltk.app.wordnet_app` 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. Commit bbaae83db86a0f49e00f5b0db44a7254c268de9b patches the issue.

Timeline

dates in UTC
  1. 2026-03-2023:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33231?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33231?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Nltk
BranchAffectedFixed in
3.9≤ 3.9.3no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • RHSA-2026:37275 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: RHOAI 3.3.5 - Red Hat OpenShift AI

  • RHSA-2026:24977 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: RHOAI 2.25.7 - Red Hat OpenShift AI

  • RHSA-2026:19712 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: RHOAI 3.3.3 - Red Hat OpenShift AI

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2026:37275 · 2 productsFor Red Hat OpenShift AI 3.3.5 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
  2. Vendor fix Red Hat Product Security RHSA-2026:24977 · 2 productsFor Red Hat OpenShift AI 2.25.7 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
  3. Vendor fix Red Hat Product Security RHSA-2026:19712 · 2 productsFor Red Hat OpenShift AI 3.3.3 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
  4. Workaround from the vendor Red Hat Product Security RHSA-2026:37275 · 235 productsTo mitigate this vulnerability, ensure that the NLTK WordNet Browser HTTP server (`nltk.app.wordnet_app`) is not exposed to untrusted networks. If the WordNet Browser functionality is not required, disable or remove the component. For deployments where the server is necessary, configure firewall ru…

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionpoc2026-03-25
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.17.5read 2026-10-23
  • CNAweakness (CWE)CWE-306read 2026-10-23
  • FIRST EPSSEPSS score1.5 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-03-20
Last Modified
2026-09-09
NVD status
Modified

Frequently asked questions

What is CVE-2026-33231?

NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. In versions 3.9.3 and prior, `nltk.app.wordnet_app` 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. Commit bbaae83db86a0f49e00f5b0db44a7254c268de9b patches the issue.

Is CVE-2026-33231 actively exploited?

A proof-of-concept exploit exists for CVE-2026-33231, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-33231?

CVE-2026-33231 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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