CVE-2026-91006Apache Karaf's instance-management service (InstanceServiceImpl) builds the command line used to launch a child Karaf JVM by string concatenation, then executes it through /bin/sh (Unix) or cscript (Windows). The caller-supplied javaOpts value is spliced into that string unquoted. A javaOpts value containing shell metacharacters (;, |, `, $(...)) is interpreted by the shell instead of being passed to the JVM as an option, giving arbitrary OS command execution as the Karaf process user.
Reachable via the shell commands instance:create, instance:start, instance:restart, instance:change-opts, and the equivalent InstanceMBean JMX operations (createInstance, startInstance, changeJavaOpts, cloneInstance).
Mitigation * Set karaf.secured.command.compulsory.roles=admin in etc/system.properties to close the fail-open gap for all unconfigured command scopes.
* Restrict which principals can reach instance:* commands and InstancesMBean via etc/users.properties role assignments.
* Treat javaOpts passed to instance:create/instance:start/instance:change-opts/InstancesMBean as untrusted input only from fully-trusted operators.