High [CVE-2026-12252] Arbitrary Code Execution via Untrusted JAR File Loading
This high-severity Red Hat Linux advisory covers CVE-2026-12252 affecting OpenShift Lightspeed.
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Summary
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. A flaw was found in the `nltk` library.
This vulnerability allows a local attacker to execute malicious code by providing an untrusted Java Archive (JAR) file, as the system lacks integrity verification for these files. Red Hat severity: Important — CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).
Weakness: CWE-347. Affected Red Hat products: OpenShift Lightspeed.
Red Hat does not currently list a fixing RHSA for this CVE.
- 3.9.3
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
Mitigation checklist
- To mitigate this issue, users should ensure that only trusted Java Archive (JAR) files are processed by the `nltk` Stanford interface classes. Avoid loading JAR files from untrusted sources, as this vulnerability allows for arbitrary code execution. Implement strict input validation and source verification for any JAR files used with `nltk` to prevent the execution of malicious code.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
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