Redhat: >> Build Of Keycloak Security Vulnerabilities
A flaw was found in Keycloak, an open-source identity and access management solution. When a user account is temporarily locked due to repeated failed login attempts, an attacker with valid client credentials can exploit the Client-Initiated Backchannel Authentication (CIBA) flow to bypass this brute-force protection. This allows continued authentication attempts and token issuance even when the account should be locked, potentially enabling further unauthorized access attempts.
CVSS Score
4.3
EPSS Score
0.001
Published
2026-05-28
A flaw was found in Keycloak. A remote attacker with high privileges, such as a realm administrator configuring a malicious Lightweight Directory Access Protocol (LDAP) server or an attacker compromising an upstream LDAP server, could exploit this vulnerability. By sending a malformed LDAP password policy response during a password authentication request, the attacker can trigger an OutOfMemoryError. This causes the Keycloak Java Virtual Machine (JVM) to terminate, leading to a denial of service (DoS) for all realms on the affected node.
CVSS Score
4.9
EPSS Score
0.002
Published
2026-05-28
A flaw was found in Keycloak. When revokeRefreshToken=true is enabled and persistent session storage is in use, a server restart can reset internal timing mechanisms. This allows a remote attacker, who has previously captured a user's refresh token, to replay that token even after it has been revoked. Successful exploitation grants the attacker unauthorized access to the victim's account, potentially leading to information disclosure or privilege escalation.
CVSS Score
6.8
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.
CVSS Score
5.3
EPSS Score
0.001
Published
2026-05-28
A flaw was found in Keycloak's Fine-Grained Admin Permissions (FGAPv2) feature. An administrator with limited client management permissions can exploit this vulnerability to assign any realm role, including highly privileged roles, to a client's scope mapping. This bypasses intended security controls, allowing the injected role to be projected into a user's authentication token when they access the modified client. This could lead to unauthorized privilege escalation within the Keycloak realm.
CVSS Score
7.3
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak. An authenticated administrator with the `manage-clients` role can exploit a Time-of-check to time-of-use (TOCTOU) vulnerability in the name-based admin role checks. This allows the attacker to escalate their privileges to `realm-admin` for all users within the realm, granting them extensive control over the system. The composite role relationship persists even after the attacker's own permissions are revoked and across system reboots.
CVSS Score
6.5
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak's Client Policies, specifically within the `org.keycloak.protocol.oidc` component. When certain condition providers (client-type, client-roles, client-attributes, client-scopes) are used to enforce security restrictions, the `reject-ropc-grant` executor is silently bypassed. This allows an unauthenticated remote attacker to obtain tokens via a Resource Owner Password Credentials (ROPC) grant, even when a policy is explicitly configured to block it. This bypass can lead to unauthorized access and information disclosure.
CVSS Score
6.5
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak. When a JSON Web Encryption (JWE) encrypted request object is submitted, Keycloak may incorrectly process unsigned claims if the decrypted content is raw JSON, bypassing the configured signature policy. This allows a remote attacker to submit unauthorized claims, leading to a compromise of data integrity within the OpenID Connect (OIDC) authorization flow. While a redirect URI allowlist acts as a compensating control, this vulnerability violates OIDC Core and Financial-grade API (FAPI) signing requirements.
CVSS Score
5.9
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak. A remote, unauthenticated attacker can exploit this vulnerability by sending specially crafted SOAP requests to the SAML ECP (Security Assertion Markup Language Enhanced Client or Proxy) endpoint with varying client IDs. By observing distinct faultstrings in the responses, the attacker can determine the client's protocol type, leading to information disclosure.
CVSS Score
5.3
EPSS Score
0.0
Published
2026-05-28
A flaw was found in Keycloak. An authenticated user with existing organization membership can exploit this flaw by accessing user-facing APIs, such as the account API or by requesting an OpenID Connect (OIDC) token with the 'organization' scope. This allows organization metadata to be disclosed in tokens, even after an administrator has explicitly disabled the Organizations feature, potentially leading to incorrect authorization decisions by resource servers.
CVSS Score
4.3
EPSS Score
0.0
Published
2026-05-28
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