OpenTelemetry Java instrumentation registers a custom RMI endpoint that deserializes incoming data without any serialization filtering. This flaw allows an attacker to send specially crafted serialized objects that, when processed by the instrumented JVM, can trigger arbitrary code execution with the privileges of the JVM process. The weakness is identified as an unsafe deserialization defect, CWE‑502. When the vulnerability is exploited, it can compromise the confidentiality, integrity, and availability of the affected system by allowing an attacker to execute arbitrary code on the host.

Products affected are the OpenTelemetry Java instrumentation libraries, versions prior to 2.26.1, when they are attached as a Java agent via the -javaagent option to a JVM running on Java 16 or earlier. The JVM must have a JMX or RMI port explicitly configured and exposed to the network, and a gadget‑chain‑compatible library must be present on the classpath. JDK versions 17 or newer are not impacted, and upgrading the instrumentation library to 2.26.1 or later removes this risk.

The CVSS score of 9.3 indicates critical severity, yet the EPSS score is below 1% and the vulnerability is not listed in the CISA KEV catalog, suggesting that real‑world exploitation is currently low. Exploitation requires three conditions at once: the JVM must be instrumented by OpenTelemetry Java instrumentation under -javaagent, a network‑reachable JMX/RMI port must be configured, and the classpath must contain a compatible gadget library. The likely attack vector is a remote attacker targeting the exposed port to deliver malicious serialized payloads; this inference is based on the description that the vulnerability can be triggered by external input over the network.