Authorization Bypass Through User-Controlled Key in Kibana Agent Builder Leading to Unauthorized Data Modification (CVE-2026-72680)

The vulnerability exists because the API endpoint derives the identifier of a stored conversation from user input and does not properly distinguish between non-existent conversations and those owned by other users. This allows an authenticated user with read privileges to overwrite another user's conversation by reusing an existing identifier, effectively reassigning ownership and deleting the original data from the victim's access.

The impact is limited to loss of integrity and availability of the affected conversation data. The attacker cannot read the overwritten content, so confidentiality is not affected. The original owner permanently loses access to the conversation and its history, which may disrupt workflows relying on that data.

A patch is available for this vulnerability. Users should apply the official fix to versions >=9.2.0 and <9.4.5 of Kibana to prevent unauthorized conversation replacement. No additional mitigation steps are indicated by the vendor advisory.