splunk-otel-javaagent: Unsafe deserialization in RMI instrumentation may lead to Remote Code Execution

In versions prior to 2.26.1, the RMI instrumentation registered a custom endpoint that deserialized incoming data without applying serialization filters. An attacker with network access to a JMX or RMI port on an instrumented JVM could exploit this to potentially achieve remote code execution. All three of the following conditions must be true to exploit this vulnerability:

1. Splunk Distribution of OpenTelemetry Java is attached as a Java agent (-javaagent)
2. An RMI endpoint is network-reachable (e.g. JMX remote port, an RMI registry, or any application-exported RMI service)
3. A gadget-chain-compatible library is present on the classpath

Impact

Arbitrary remote code execution with the privileges of the user running the instrumented JVM.

Recommendation

Upgrade to version 2.26.1 or later.

Workarounds

Set the following system property to disable the RMI integration:

-Dotel.instrumentation.rmi.enabled=false

References

Advisory in OpenTelemetry Instrumentation for Java