CVE-2026-18572 in Keycloak
Summary
by MITRE • 08/02/2026
Keycloak provides authorization services that allow administrators to restrict access to resources based on time policies (for example, only allowing access during business hours). A flaw was discovered where a user can include a fake time value in their authorization request that overrides the actual server time. This allows the user to bypass these time-based restrictions and access protected resources at unauthorized times.
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Analysis
by VulDB Data Team • 08/02/2026
This vulnerability resides within Keycloak's authorization service implementation where time-based access control mechanisms are compromised through malicious manipulation of authorization requests. The flaw represents a critical authorization bypass issue that directly undermines the integrity of time-sensitive resource protection policies. When administrators configure time-based restrictions to limit access to specific periods such as business hours, the system fails to properly validate time values submitted by users during authentication requests. This weakness allows authenticated users to inject falsified temporal data into their authorization tokens or requests, effectively overriding legitimate server-side time checks and enabling access outside permitted time windows.
The technical implementation flaw stems from insufficient input validation and trust assumptions within Keycloak's authorization framework. Attackers can manipulate time values in authorization requests without proper server-side verification, creating a privilege escalation scenario where users gain unauthorized access to protected resources during non-permitted time periods. This vulnerability operates at the intersection of authentication and authorization controls, specifically targeting the temporal validation logic that should enforce policy compliance. The flaw demonstrates a classic case of inadequate trust boundaries where client-provided data is not properly sanitized or validated against server-side authoritative time sources.
From an operational impact perspective, this vulnerability enables persistent unauthorized access to sensitive resources during restricted time periods, potentially compromising security policies designed to limit access windows. Organizations relying on Keycloak's time-based restrictions for compliance requirements, data protection, or operational security may experience significant breaches when attackers exploit this flaw to access systems outside designated business hours. The vulnerability affects any deployment where administrators have configured time-based access controls, making it particularly concerning for environments with strict regulatory compliance requirements such as financial services, healthcare, or government sectors.
This issue aligns with CWE-284 Access Control Bypass and specifically relates to improper authorization validation mechanisms that fail to enforce time-based policy constraints. The vulnerability also maps to ATT&CK technique T1078 Valid Accounts, where attackers leverage legitimate authentication tokens to access resources outside normal operational parameters. Organizations should implement immediate mitigations including server-side time validation enforcement, input sanitization of temporal parameters in authorization requests, and enhanced monitoring for anomalous access patterns during restricted time periods.
Recommended remediation strategies include enforcing strict time value validation that rejects any client-provided temporal data and relies exclusively on server-side authoritative time sources, implementing comprehensive logging of access attempts with temporal metadata, and upgrading to patched versions of Keycloak that address this authorization bypass vulnerability. Additional defensive measures should include regular security assessments of authorization policies, implementation of continuous monitoring for unauthorized access during restricted periods, and configuration reviews to ensure time-based restrictions are properly enforced without client-side overrides. Organizations should also consider implementing additional layers of access control such as network segmentation and behavioral analytics to detect and prevent exploitation attempts targeting this vulnerability.