# CVE-2026-79675: NLTK JVM argument injection bypass in Stanford wrappers

Source: https://junglewise.ai/threats/cve-2026-79675-nltk-jvm-argument-injection-bypass-in-stanford-wrappers  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-79675 · Severity: critical · CVSS 9.8 · Published 2026-08-25

NLTK is a Python library for natural language processing that includes wrapper classes to invoke Stanford NLP tools via Java. A previous fix for JVM argument injection was incomplete, validating only global configuration but not per-call options. An attacker can bypass this validation by passing malicious JVM flags (like `-agentpath` or `-javaagent`) through the `java_options` parameter of Stanford wrapper classes, achieving arbitrary code execution on the server running NLTK.

Technologies: [nltk (PyPI)](https://junglewise.ai/threats/technologies/nltk). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-79675 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79675 being exploited in the wild.

**How severe is CVE-2026-79675?** Critical severity, with a CVSS score of 9.8, published 25 August 2026.

**Which products and versions are affected?** nltk (PyPI) <= 3.10.2, ECOSYSTEM:introduced=0,fixed=3.10.3.

**Is there a fix for CVE-2026-79675?** Yes. nltk (PyPI): upgrade to 3.10.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-79675 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-79675?** Check whether you run nltk (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- nltk (PyPI): upgrade to 3.10.3 or later

  ```sh
  pip install "nltk>=3.10.3"
  ```


## Technical details

This is a CWE-88 argument injection vulnerability affecting the `java()` function in `nltk/internals.py`. The root cause is that while `config_java()` validates JVM options via `_validate_java_options()`, the `java()` function's per-call `options` parameter (added in PR #3683) bypasses this validation entirely and passes options directly to `subprocess.Popen`. All four Stanford wrapper classes (GenericStanfordParser, StanfordTagger, StanfordTokenizer, StanfordSegmenter) accept user-supplied `java_options` and route them through this unvalidated path. An attacker controlling the `java_options` parameter can inject dangerous flags including `-agentpath:/path/to/malicious.so` (native code execution), `-javaagent:/path/to/malicious.jar` (bytecode manipulation), `-agentlib:jdwp` (remote debugging), or `@argfile` (argument expansion). The vulnerability is exploitable in services where `java_options` derives from user input, configuration files, or environment variables. A patch is available in version 3.10.3 and later via a single-line addition calling `_validate_java_options()` on per-call options.

## Affected products

- NLTK Project NLTK <= 3.10.2

## Identifiers

- CVE-2026-79675
- GHSA-m4rf-3fr8-xwx3
- PYSEC-2026-3749

## Timeline

- 2026-09-01: disclosed: Advisory published
- 2026-09-01: patched: Version 3.10.3 released with fix
- 2026-08-11: other: Advisory initially published on GitHub

## References

- [https://api.github.com/users/arpitjain099](https://api.github.com/users/arpitjain099)
- [https://github.com/arpitjain099](https://github.com/arpitjain099)
- [https://api.github.com/users/arpitjain099/gists%7B/gist_id%7D](https://api.github.com/users/arpitjain099/gists%7B/gist_id%7D)
- [https://api.github.com/users/arpitjain099/repos](https://api.github.com/users/arpitjain099/repos)
- [https://avatars.githubusercontent.com/u/3242828?v=4](https://avatars.githubusercontent.com/u/3242828?v=4)
- [https://api.github.com/users/arpitjain099/events%7B/privacy%7D](https://api.github.com/users/arpitjain099/events%7B/privacy%7D)

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- [NLTK RecursiveDescentParser uncontrolled recursion denial of service](https://junglewise.ai/threats/cve-2026-12876-nltk-recursivedescentparser-uncontrolled-recursion-denial-of)
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