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    CVE-2026-9803

    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.

    Published:May 28, 2026
    Last Modified:Jun 26, 2026
    EPS:May 28, 2026
    EPSS Score:0.00389
    CVSS Score:5.3

    Affected Products

    Vendor
    Redhat
    Product
    Build Keycloak
    Vendor
    Redhat
    Product
    Build Of Keycloak
    Vendor
    Redhat
    Product
    Keycloak

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-125 Out-of-bounds Read

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-540 Overread Buffers

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High