CVE-2026-63317

Name of the Vulnerable Software and Affected Versions Apache OpenNLP versions prior to 2.5.10 Apache OpenNLP versions prior to 3.0.0-M5

Description Three code paths allow arbitrary class instantiation by loading a class via its fully-qualified name using Class.forName() and invoking its no-arg constructor without prior validation. The affected paths include GeneratorFactory, which processes the class attribute of generator elements in XML feature generator descriptors embedded in model archives; StreamFactoryRegistry.getFactory(Class, String), which may interpret an unregistered format name as a class name for an ObjectStreamFactory; and StringInterners, which uses the opennlp.interner.class system property. Exploitation requires a class with side effects in its static initializer or no-arg constructor to be present on the classpath.

Recommendations Upgrade to version 2.5.10 or later. Upgrade to version 3.0.0-M5 or later. For deployments requiring factories or interners outside the opennlp.* prefix, use ExtensionLoader.registerAllowedPackage(String) or set the OPENNLP EXT ALLOWED PACKAGES system property to a comma-separated list of allowed package prefixes. Ensure all model files and format names are sourced from trusted origins. Audit the classpath for classes with side-effecting static initializers or constructors.