Red Hat Keycloak/Single Sign-On Dynamic Client Registration defaultRoles improper authorization

Summaryinfo

A vulnerability has been found in Red Hat Keycloak and Single Sign-On and classified as problematic. Affected is an unknown function of the component Dynamic Client Registration. This manipulation of the argument defaultRoles causes improper authorization. The identification of this vulnerability is CVE-2026-109081. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as problematic was found in Red Hat Keycloak and Single Sign-On (the affected version unknown). Affected by this vulnerability is an unknown part of the component Dynamic Client Registration. The manipulation of the argument defaultRoles with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect availability. The summary by CVE is:

A flaw was found in Keycloak. The Dynamic Client Registration (DCR) endpoint does not properly validate authorization when processing the deprecated defaultRoles field. An authenticated attacker with client creation privileges or an Initial Access Token (IAT) can inject excessive roles into the realm's default roles configuration. This causes clients across the realm to generate bloated access tokens, resulting in performance and memory degradation that can lead to a Denial of Service (DoS).

The advisory is shared at access.redhat.com. This vulnerability is known as CVE-2026-109081 since 10/12/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are needed for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 11/06/2026). MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Red Hat

Name

• Keycloak
• Single Sign-On

License

• open-source

Website

• Vendor: https://www.redhat.com/

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