CVE-2026-9099: A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated...

Description

A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated user with limited administrative privileges to reparent any existing group. When Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, an attacker with management rights over a single low-privilege group can reparent a highly privileged group (such as one possessing the realm-admin role) under their managed group. Because group permissions follow a hierarchical structure, this action unauthorizedly grants the attacker management and password-reset capabilities over the members of the targeted privileged group. An attacker can exploit this to reset an administrator's password, compromise the account, and achieve a full realm takeover, leading to a complete compromise of confidentiality, integrity, and availability.

Metrics

CVSS 3.1

7.7/10

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N

EPSS Probability

0.27%

18.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-639

References

Timeline

Published: Jun 25, 2026
Last Modified: Jun 26, 2026
Status: Undergoing Analysis

Frequently Asked Questions

What is CVE-2026-9099?

A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated user with limited administrative privileges to reparent any existing group. When Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, an attacker with management rights over a single low-privilege group can reparent a highly privileged group (such as one possessing the realm-admin role) under their managed group. Because group permissions follow a hierarchical structure, this action unauthorizedly grants the attacker management and password-reset capabilities over the members of the targeted privileged group. An attacker can exploit this to reset an administrator's password, compromise the account, and achieve a full realm takeover, leading to a complete compromise of confidentiality, integrity, and availability.

How severe is CVE-2026-9099?

CVE-2026-9099 has a CVSS score of 7.7/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.

How do I fix CVE-2026-9099?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.