CVE-2026-72643 in Kibana
Summary
by MITRE • 08/13/2026
Kibana Agent Builder determines whether a caller owns a private agent by comparing a stable user identifier when one is recorded, and falling back to a comparison of the username when it is not. A username is not unique across Elasticsearch authentication realms, so two distinct principals that share a username in different realms are treated as the same owner. This discloses the configuration and instructions of an agent the caller does not own, and allows that agent to be altered or removed.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability exists within Kibana's Agent Builder functionality where the system employs a flawed ownership verification mechanism that can lead to privilege escalation and unauthorized access to sensitive agent configurations. The core technical flaw stems from how the system determines agent ownership by first attempting to match a stable user identifier when available, but falling back to username comparison as a secondary validation method when no stable identifier exists. This design creates a critical security weakness because usernames are not guaranteed to be unique across different authentication realms within Elasticsearch, allowing malicious actors to exploit this inconsistency for unauthorized access.
The operational impact of this vulnerability is significant as it enables attackers to bypass legitimate ownership checks and gain access to agent configurations that they should not have permission to view or modify. When two distinct user principals share the same username but exist in different authentication realms, the system incorrectly treats them as identical owners, leading to information disclosure of private agent details including configuration parameters, deployment instructions, and operational settings. This flaw effectively undermines the principle of least privilege and can result in complete compromise of agent management capabilities.
The vulnerability directly relates to CWE-284: Improper Access Control, which specifically addresses insufficient access control mechanisms that allow unauthorized users to gain privileges or access resources they should not be permitted to access. From an ATT&CK framework perspective, this represents a privilege escalation technique under T1078: Valid Accounts, where attackers leverage legitimate credentials from one realm to impersonate users in another realm and gain unauthorized access to system resources. The issue also aligns with T1566: Phishing, as it could be exploited through credential compromise scenarios where attackers obtain valid usernames from one authentication domain.
Security mitigations should focus on implementing stronger user identification mechanisms that do not rely solely on potentially non-unique username attributes. Organizations should ensure that stable user identifiers are consistently maintained and utilized for ownership verification rather than falling back to username comparisons. The system architecture must enforce unique identification across all authentication realms, potentially through the implementation of universally unique identifiers or additional contextual validation factors such as authentication source information. Regular security audits should verify that no two distinct users can share identical usernames across different realms, and access control policies should be reviewed to ensure proper segregation between authentication domains. Additionally, implementing comprehensive logging and monitoring around agent ownership verification attempts will help detect potential exploitation attempts and provide forensic evidence for incident response activities.
This vulnerability demonstrates the critical importance of maintaining unique user identification mechanisms in distributed authentication systems where multiple realms coexist, as the failure to properly distinguish between users can lead to complete compromise of access control protections. The flaw serves as a reminder that seemingly minor implementation details in authentication systems can have far-reaching security implications when dealing with complex multi-realm environments.