Bug 2508292 (CVE-2026-18206)

Summary: CVE-2026-18206 keycloak-services: keycloak-services: Client policy source-host wildcard domain matching bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: anujha, aschwart, asoldano, aszczucz, bbaranow, bmaxwell, boliveir, bstansbe, dlofthou, drichtar, istudens, ivassile, iweiss, mosmerov, mposolda, msvehla, nwallace, pberan, pesilva, pjindal, pmackay, rmartinc, rstancel, ssilvert, sthorger, thjenkin, vdosoudi, vmuzikar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the keycloak-services component of Keycloak, which provides identity and access management services. The issue occurs when a realm administrator uses a wildcard domain (like *.example.com) to restrict which hosts can register or update clients. Due to improper validation, the system accepts any hostname that ends with the specified domain suffix, even if it is not a legitimate subdomain. An attacker who can control the reverse DNS of their connection can bypass these host-based restrictions, potentially allowing unauthorized client modifications.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-29 07:56:49 UTC 
A flaw was found in the hostname matching logic within the ClientUpdaterSourceHostsCondition of Keycloak. When a wildcard domain (e.g., *.example.com) is configured as a trusted source host in a client policy, the matching mechanism performs a simple suffix check without ensuring a proper subdomain boundary (a preceding dot).
An unauthenticated attacker whose connecting IP address reverse-resolves to a crafted hostname ending in the trusted suffix (e.g., attackerexample.com) can satisfy the condition. This allows the attacker to bypass source-host restrictions intended to limit client registration or update operations to trusted domains. Successful exploitation causes policy executors to run as if the request originated from a legitimate trusted source, which can weaken or bypass security constraints applied to client management.