Quick answers
- Is CVE-2026-12252 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-12252 being exploited in the wild.
- How severe is CVE-2026-12252?
- High severity, with a CVSS score of 7.8, published 4 July 2026.
- Which products and versions are affected?
- nltk (PyPI) < 3.9.4, ECOSYSTEM:introduced=0,fixed=3.9.4.
- Is there a fix for CVE-2026-12252?
- Yes. nltk (PyPI): upgrade to 3.9.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-12252 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-12252?
- 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 3.9.4 or later
pip install "nltk>=3.9.4"
Technical details
A code injection vulnerability exists in NLTK's Stanford interface classes, including StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser. These classes accept user-controllable JAR paths and execute them using the `java()` function, which internally calls `subprocess.Popen()` without verifying the JAR's integrity or origin. While a similar issue was previously patched in the StanfordSegmenter class using SHA256 verification, these specific classes remained unpatched. An attacker can achieve arbitrary code execution if they can convince a user to point the library at a malicious JAR file.
Affected products
- nltk nltk <= 3.9.3
Identifiers
- CVE-2026-12252
- GHSA-9r6g-266r-89x4
- PYSEC-2026-2085
Timeline
- 2026-07-04: advisory: NVD publication date