Summary
OpenTelemetry: 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:
- OpenTelemetry Java instrumentation is attached as a Java agent (
-javaagent) - An RMI endpoint is network-reachable (e.g. JMX remote port, an RMI registry, or any application-exported RMI service)
- A gadget-chain-compatible library is present on the classpath
Workarounds
Set the following system property to disable the RMI integration:
-Dotel.instrumentation.rmi.enabled=false
Credits
This vulnerability was responsibly disclosed in coordination with Datadog.
Impact
Arbitrary remote code execution with the privileges of the user running the instrumented JVM.
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
CVE-2026-33701 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.26.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Upgrade to version 2.26.1 or later.
Frequently Asked Questions
- What is CVE-2026-33701? CVE-2026-33701 is a critical-severity insecure deserialization vulnerability in io.opentelemetry.javaagent:opentelemetry-javaagent (maven), affecting versions < 2.26.1. It is fixed in 2.26.1. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- How severe is CVE-2026-33701? CVE-2026-33701 has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of io.opentelemetry.javaagent:opentelemetry-javaagent are affected by CVE-2026-33701? io.opentelemetry.javaagent:opentelemetry-javaagent (maven) versions < 2.26.1 is affected.
- Is there a fix for CVE-2026-33701? Yes. CVE-2026-33701 is fixed in 2.26.1. Upgrade to this version or later.
- Is CVE-2026-33701 exploitable, and should I be worried? Whether CVE-2026-33701 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33701 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33701? Upgrade
io.opentelemetry.javaagent:opentelemetry-javaagentto 2.26.1 or later.