CVE-2026-43825

Untrusted Java Deserialization in Apache OpenNLP SvmDoccatModel

Versions Affected:

  before 3.0.0-M4 (libsvm document categorization module; introduced in

  OPENNLP-1808 and only present on the 3.x line)

Description:

SvmDoccatModel.deserialize(InputStream) reads an attacker-controlled

stream with java.io.ObjectInputStream and calls readObject() without an

ObjectInputFilter installed. ObjectInputStream materialises every class

referenced in the stream before the resulting object is cast to

SvmDoccatModel, so the cast that follows readObject() executes only

after the foreign object graph has already been deserialised in full.

If a Java deserialization gadget chain is available on the consumer's

classpath, a crafted payload supplied to

deserialize() executes arbitrary code in the JVM that loads it. Apache

OpenNLP itself does not ship a known gadget chain, so the realistic

risk is to downstream applications that embed the libsvm module

alongside vulnerable transitive dependencies. The method is public and

static, so any caller can pass an untrusted stream to it directly.

The practical impact is remote code execution against processes that

load SvmDoccatModel instances from untrusted or semi-trusted origins.

Mitigation:

3.x users should upgrade to 3.0.0-M4.

Users who cannot upgrade immediately should treat all serialized

SvmDoccatModel streams as untrusted input unless their provenance is

verified, and should avoid invoking SvmDoccatModel.deserialize() on

streams supplied by end users or fetched from third-party sources

without integrity checks.