CVE-2026-12252: nltk Code Injection — Exploit

Description

In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser) are vulnerable to untrusted JAR code execution. These classes accept user-controllable JAR paths and execute them via the `java()` function, which invokes `subprocess.Popen()` without integrity verification. This vulnerability is identical to CVE-2026-0848, which was fixed for StanfordSegmenter by adding SHA256 verification. However, the fix was not applied to these additional classes, leaving them susceptible to arbitrary code execution when loading untrusted JAR files.

Is your site exposed to CVE-2026-12252?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

7.8

HIGH

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0016

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-94 CWE-94

Affected Products

Vendor	Product	Versions
nltk	nltk	< 3.9.3

References

Exploits

https://huntr.com/bounties/f5c93982-0cc9-4e2e-bb85-1b6ab29a2efb https://huntr.com/bounties/f5c93982-0cc9-4e2e-bb85-1b6ab29a2efb

Frequently Asked Questions

What is CVE-2026-12252? +

In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser) are vulnerable to untrusted JAR code execution. These classes accept user-controllable JAR paths and execute them via the `java()` function, which invokes `subprocess.Popen()` without integrity verification. This vulnerability is identical to CVE-2026-0848, which was fixed for StanfordSegmenter by adding SHA256 verification. However, the fix was not applied to these additional classes, leaving them susceptible to arbitrary code execution when loading untrusted JAR files. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2026-12252? +

CVE-2026-12252 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0016, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-12252? +

CVE-2026-12252 affects products from nltk, specifically: nltk. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-12252? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-22136

Tabby (formerly Terminus) is a highly configurable terminal emulator. Prior to 1.0.217 , Tabby enables several high-risk Electron Fuses, including …

CVE-2025-24482

A Local Code Injection Vulnerability exists in the product and version listed above. The vulnerability is due to incorrect default …

CVE-2026-55576

MaaAssistantArknights is a one-click tool for daily Arknights tasks. In the current dev-v2 workflow, .github/workflows/release-preparation.yml inlined attacker-controlled github.event.pull_request.title into a …

CVE-2026-59859

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.32.4, Kiota's PHP generator embedded OpenAPI description, default fields, …

CVE-2026-59865

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.32.5, `kiota info` read x-ms-kiota-info.languagesInformation.<language>.dependencyInstallCommand plus dependency name and …

CVE-2026-42890

Actual is an open-source personal finance application. In the macOS desktop application version 25.x (built on Electron 39.2.7), the ELECTRON_RUN_AS_NODE …

CVE-2026-12252