EUVD-2026-51486
GHSA-2w88-g477-cxmj
Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Network-reachable but AC:H due to required reverse DNS control; no credentials needed; only limited client-configuration integrity impact, no confidentiality or availability effect.
Primary rating from Vendor (redhat).
CVSS VectorNVD
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Lifecycle Timeline
2DescriptionNVD
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.
AnalysisAI
Wildcard domain validation in Keycloak's keycloak-services component can be bypassed by an attacker who controls their connection's reverse DNS, enabling unauthorized client registration or modification against a Keycloak realm. The flaw stems from the system accepting any hostname that merely ends with the configured domain suffix (e.g., 'attackerexample.com' satisfying a '*.example.com' restriction) rather than enforcing true subdomain membership. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires two concurrent conditions: (1) a realm administrator must have configured a wildcard domain pattern (e.g., '*.example.com') in the client registration or client update host restriction policy - this is not a default Keycloak configuration; (2) the attacker must control the reverse DNS (PTR record) of the IP address from which they are connecting, enabling them to present a hostname that ends with the configured domain suffix without being a legitimate subdomain. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 3.1 score of 3.7 (Low) reflects the narrow real-world risk profile accurately. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who owns a server with a PTR record resolving to 'attackerexample.com' targets a Keycloak realm configured with a '*.example.com' wildcard host restriction. By connecting from that server, the attacker's hostname passes the suffix-based validation check and is permitted to register or modify OAuth/OIDC clients in the realm. … |
| Remediation | Patch availability per vendor advisory: a patch is available per Red Hat advisory (https://access.redhat.com/security/cve/CVE-2026-18206), but an exact patched version number is not confirmed in the available intelligence - consult the Red Hat advisory and Bugzilla entry (https://bugzilla.redhat.com/show_bug.cgi?id=2508292) for the specific fixed build. … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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