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CVE-2026-91006: Apache Karaf: OS Command Injection in Child-Instance Launch (instance:* / InstancesMBean)

Severity: moderate 

Affected versions:

- - Apache Karaf (org.apache.karaf:org.apache.karaf.instance.core) before 4.4.12

Description:

Apache 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.

This issue is being tracked as https://github.com/apache/karaf/pull/2878 

Credit:

n0mi1k <nomilksec@gmail.com> (reporter)

References:

https://karaf.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-91006
https://github.com/apache/karaf/pull/2878

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