CVE-2026-16089 in Build of Keycloak
Summary
by MITRE • 07/17/2026
A flaw was found in the keycloak-services component of Red Hat Build of Keycloak. The issue occurs because OAuth 2.0 authorization codes are not properly bound to the client that originally requested them. An attacker who can intercept an authorization code can modify it to be redeemed by their own client, potentially allowing them to obtain access tokens for a victim's identity.
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Analysis
by VulDB Data Team • 07/17/2026
This vulnerability resides within the keycloak-services component of Red Hat Build of Keycloak, representing a critical security flaw that undermines the fundamental integrity of the OAuth 2.0 authorization flow. The weakness stems from improper binding of OAuth 2.0 authorization codes to their originating clients, creating a scenario where authorization codes can be intercepted and maliciously transferred between different client applications. This represents a direct violation of OAuth 2.0 security principles that mandate strict binding between authorization requests and their corresponding responses to prevent unauthorized code reuse.
The technical implementation flaw allows attackers to exploit the lack of proper client binding mechanisms by intercepting valid authorization codes during transmission. When an attacker successfully intercepts such a code, they can manipulate it to be redeemed by their own malicious client application rather than the legitimate one that originally requested it. This creates a privilege escalation scenario where unauthorized parties can obtain access tokens that authenticate as legitimate users, effectively impersonating victims within the Keycloak authentication ecosystem. The vulnerability directly maps to CWE-287, which addresses improper authentication mechanisms and authorization code binding failures in authentication protocols.
The operational impact of this vulnerability extends beyond simple credential theft, potentially enabling comprehensive account takeover scenarios and unauthorized access to protected resources. Attackers can leverage this flaw to gain persistent access to user accounts, escalate privileges within the Keycloak environment, and compromise the integrity of the entire authentication infrastructure. The implications are particularly severe in enterprise environments where Keycloak serves as a central identity management solution for multiple applications and services. This vulnerability aligns with ATT&CK technique T1566, which covers credential harvesting through phishing and social engineering attacks, but specifically exploits weaknesses in the authorization code handling rather than traditional phishing vectors.
Mitigation strategies should focus on implementing proper client binding verification mechanisms that ensure authorization codes can only be redeemed by the specific client that requested them. Organizations must immediately apply available patches from Red Hat that address this specific vulnerability in the keycloak-services component. Additionally, network monitoring should be enhanced to detect unusual patterns in authorization code usage and redemption. Security teams should implement strict validation checks that verify the client identifier associated with each authorization code before allowing token redemption. The recommended approach includes enabling additional security controls such as PKCE (Proof Key for Code Exchange) when available, which provides an additional layer of protection against authorization code interception and misuse. Organizations should also consider implementing rate limiting and anomaly detection mechanisms to identify potential exploitation attempts and maintain comprehensive audit logs for forensic analysis.