Red Hat Security Advisory: Red Hat build of Keycloak 26.6.4 Security Update
🔗 CVE IDs covered (17)
📋 Description
CVE-2026-6860 — eclipse-vertx/vert.x: eclipse-vertx/vert.x: Denial of Service via TLS handshake with wildcard server name CVE-2026-9083 — keycloak: Keycloak: Information disclosure through arbitrary filesystem path probing CVE-2026-9086 — keycloak: Keycloak: Cross-site scripting (XSS) via case-insensitive URI validation bypass CVE-2026-9099 — keycloak: Group-Admin Escalation to Realm-Admin CVE-2026-9705 — keycloak: Keycloak: Attacker can re-enable and take over disabled clients via Registration Access Token CVE-2026-9795 — keycloak: Keycloak: Privilege escalation via improper scope mapping enforcement CVE-2026-9799 — keycloak: Keycloak: Unauthorized access to resources via UMA permission ticket bypass CVE-2026-9800 — keycloak-policy-enforcer: Keycloak Policy Enforcer: Authorization bypass via incorrect URI comparison CVE-2026-11800 — org.keycloak:keycloak-services: Keycloak: Authentication bypass via JWT algorithm confusion CVE-2026-44249 — netty-handler: netty-handler: IPv6 subnet rule bypass due to incorrect masking operation CVE-2026-44893 — netty-codec-haproxy: Netty-codec-haproxy: Denial of Service via malformed HAProxy message CVE-2026-45416 — netty-handler: Netty: Denial of Service due to eager buffer allocation in TLS handshake CVE-2026-45674 — netty-resolver-dns: Netty: Information disclosure and data manipulation due to improper CNAME record validation CVE-2026-47691 — io.netty/netty-resolver-dns: Netty has Insufficient Bailiwick Validation for NS Records CVE-2026-48043 — netty-codec-http2: netty-codec-http2: Denial of Service due to resource leak CVE-2026-48059 — netty-codec-haproxy: Netty HAProxy PROXY protocol v2 codec: Denial of Service via memory leak from crafted PROXY protocol headers CVE-2026-50010 — netty-handler: Netty: Improper trust manager handling leads to hostname verification bypass
🎯 Affected products1
- Red Hat build of Keycloak 26.6.4
✅ Remediation
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on. Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Workaround: Ensure that only highly trusted administrators are granted the "manage-realm" role within Keycloak. This role provides extensive administrative privileges, including the ability to exploit this vulnerability for filesystem probing. Regularly review and audit users assigned to this role to minimize the attack surface. Workaround: To mitigate this vulnerability, restrict the ability to register new clients and manage existing client configurations. If Dynamic Client Registration is not required, disable it in Keycloak's Realm Settings under Client Registration Policies. If Dynamic Client Registration is necessary, ensure that policies are strictly configured to prevent anonymous client registration and require initial access tokens for all client registrations. Additionally, limit the `manage-client` role to only trusted administrators. Changes to Keycloak configuration may require a service restart or redeployment to take effect. Workaround: To mitigate this issue, restrict network access to the Keycloak Admin REST API to only trusted networks or localhost. This limits the attack surface by preventing unauthorized access to the API endpoints required for exploitation. Consult your network security documentation for specific firewall or network access control configurations. This may impact remote administration capabilities. Workaround: To mitigate this issue, restrict network access to the Keycloak Dynamic Client Registration endpoint. Configure network firewalls to allow connections only from trusted hosts or networks that legitimately require access to this functionality. This limits the exposure of the vulnerable endpoint to unauthorized access attempts. Workaround: To mitigate this issue, disable the Fine-Grained Admin Permissions (FGAPv2) feature in Keycloak if it is not strictly required. This can typically be done by setting `adminPermissionsEnabled` to `false` in the realm configuration. Disabling FGAPv2 will prevent the exploitation of this flaw by removing the vulnerable functionality. However, this may impact administrative delegation capabilities within Keycloak. A restart or reload of the Keycloak service may be required for the changes to take effect. Workaround: To mitigate this issue, ensure that the Keycloak client's policy enforcement mode is set to ENFORCING instead of PERMISSIVE. The PERMISSIVE mode is a non-default configuration that enables the vulnerability. Changing this setting will prevent the unauthorized access to resources of the same type. Consult Keycloak documentation for specific instructions on configuring policy enforcement mode for your client. This change may require a restart or reload of the Keycloak service to take effect and could impact existing authorization policies if not carefully managed. Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Workaround: To mitigate this issue, configure applications utilizing Netty's `SslClientHelloHandler` to specify a non-zero value for the `maxClientHelloLength` parameter. This will enable the internal length validation, preventing the eager allocation of large memory buffers when processing crafted TLS ClientHello messages. Refer to your specific application's documentation for details on configuring Netty's TLS handler. A restart of the affected application or service is required for the configuration changes to take effect.