CVE-2026-91012org.apache.karaf.config.core.impl.ConfigRepositoryImpl#update(pid, properties),
which backs the "config" MBean and the config:* shell commands, derives the file
it writes a configuration to from caller-supplied input without checking that
the result stays inside ${karaf.etc}:
* if the submitted property map contains a felix.fileinstall.filename entry, that value is turned directly into a File (getCfgFileFromProperty), so it can point to any absolute path the Karaf process can write to;
* otherwise the configuration PID is concatenated verbatim into the target file name (generateConfigFilename(): new File(karaf.etc, pid + ".cfg")), so a PID containing ".." segments resolves outside ${karaf.etc}. createFactoryConfiguration() has the same issue via the factory PID/alias.
Both code paths are reachable by any caller holding the "manager" role under Karaf's shipped command/JMX ACL (org.apache.karaf.command.acl.conf.cfg: "update = manager"). Such a user can therefore write attacker-controlled content to any file the Karaf process can write, including files the same ACL otherwise reserves to "admin" (etc/users.properties, etc/*.acl.*.cfg, etc/org.apache.karaf.management.cfg, and similar), allowing a manager-role user to grant themselves the admin role or otherwise take over the container.
ConfigMBeanImpl.install() and the config:install shell command already guarded the equivalent risk on their own code path with a finalname.contains("..") string check, but that check does not stop absolute paths or symlink-based escapes, and it was never applied to ConfigRepositoryImpl.update() / createFactoryConfiguration() at all.