Kibana Agent Builder fails to correctly verify ownership of a private agent by comparing a stable user identifier only when one is stored, otherwise falling back to a comparison of usernames. Because usernames are not unique across Elasticsearch authentication realms, two distinct principals that share a username in different realms are treated as the same owner. This flaw allows a user who does not own the agent to view its configuration and instructions and to alter or remove the agent, thereby compromising confidentiality, integrity, and potentially availability of the service.

Elastic Kibana installations that expose the Agent Builder functionality are affected. The vulnerability is tied to the ownership verification logic and is not limited to a specific product line. No specific version range is provided in the advisory, so any deployment that uses this code path is potentially vulnerable.

The CVSS score of 7.1 indicates medium to high severity. No EPSS score is available, and the vulnerability is not listed in CISA KEV, suggesting no known widespread exploitation yet. Attackers can exploit the flaw by authenticating to the Kibana interface with an account that shares a username with another realm’s principal. Once authenticated, the attacker can read and modify private agent details, leading to unauthorized configuration changes or data exposure. The likely attack vector is web-based and requires valid Kibana credentials.