CVE-2026-33236 NLTK has a Downloader Path Traversal Vulnerability (AFO) - Arbitrary File Overwrite
Attackers can exploit path traversal in NLTK downloader to overwrite arbitrary files, potentially leading to code execution.
- 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-2026-33236?
CVE-2026-33236 is a high-severity path traversal 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, the NLTK downloader does not validate the `subdir` and `id` attributes when processing remote XML index files. Attackers can control a remote XML index server to provide malicious values containing path traversal sequences (such as `../`), which can lead to arbitrary directory creation, arbitrary file creation, and arbitrary file overwrite. Commit 89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a patches the issue.
Weakness: CWE-22
Which versions are affected by CVE-2026-33236?
3 open source packages ship an affected version, including nltk. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nltk PyPI | All versions to 3.9.2 | None |
nltk PyPI | All versions to 3.9.2 | None |
nltk PyPI | All versions | 3.9.4 |
Products include Nltk Nltk.
How do I fix CVE-2026-33236?
Upgrade nltk to 3.9.4 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-33236 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33236 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-2026-33236, ECHO-85d4-7fa8-a8c9, GHSA-469j-vmhf-r6v7, PYSEC-2026-2237, ROOT-APP-PYPI-CVE-2026-33236.