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VulnerabilityPublished

CVE-2026-12199: nltk/nltk · Missing Authentication

Affects nltk/nltkSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.9.4 soon.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.0 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.9.4
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 17 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade nltk to 3.9.4.

Affected software

ProductAffectedFixed in
nltknltk/nltkAffected
  • ≥ unspecified, ≤ latest
Fixed in–
PyPInltkpkg:pypi/nltkOther threatsAffected
  • <3.9.4
Fixed in
  • 3.9.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users should avoid exposing the WordNet Browser HTTP server to untrusted networks or restrict access to trusted hosts only. Consider disabling or not using the server in default mode if remote access is not required.

Description

A vulnerability in nltk's WordNet Browser HTTP server (up to version 3.9.3) allows unauthenticated remote shutdown via a specific GET request, causing denial of service. The server listens on all interfaces and lacks authentication for this critical function. This issue impacts service availability by terminating the server process immediately.

References

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