CVE-2026-33230 nltk Vulnerable to Cross-site Scripting
Attackers can execute arbitrary JavaScript in the browser of users running the local NLTK WordNet Browser server via a crafted URL.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-33230?
CVE-2026-33230 is a medium-severity cross-site scripting vulnerability in nltk, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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` contains a reflected cross-site scripting issue in the `lookup_...` route. A crafted `lookup_<payload>` URL can inject arbitrary HTML/JavaScript into the response page because attacker-controlled `word` data is reflected into HTML without escaping. This impacts users running the local WordNet Browser server and can lead to script execution in the browser origin of that application. Commit 1c3f799607eeb088cab2491dcf806ae83c29ad8f fixes the issue.
Weakness: CWE-79
Which versions are affected by CVE-2026-33230?
3 open source packages ship an affected version, including nltk. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nltk PyPI | All versions | 3.9.4 |
nltk PyPI | All versions | 3.9.4 |
nltk PyPI | All versions | 3.9.4 |
Linux distribution packages (1)
python-nltk openSUSE:Tumbleweed | All versions | 3.9.4-1.1 |
Products include Nltk Nltk.
How do I fix CVE-2026-33230?
Upgrade nltk to 3.9.4 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-33230 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33230 exists.
Other vulnerabilities in nltk
- CVE-2026-0848 Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading
- CVE-2025-14009 Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution
- CVE-2026-78683 NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization
- CVE-2026-79657 NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization
- CVE-2026-79675 NLTK before 3.10.3 JVM Argument Injection via Per-Call Options
Sources
Also known as DEBIAN-CVE-2026-33230, ECHO-71be-89bb-7761, GHSA-gfwx-w7gr-fvh7, MGASA-2026-0082, MINI-2m5f-4f52-x27m, PYSEC-2026-2235 and 4 more.