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CVE-2026-18206— Keycloak-services: keycloak-services: client policy source-host wildcard domain matching bypass

Quick assessment

Affected
Red Hat Red Hat Build of Keycloak
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Keycloak是Keycloak组织开源的一种身份和访问管理解决方案。 Keycloak存在输入验证错误漏洞，该漏洞源于通配符域名的验证不当，系统接受任何以指定域名后缀结尾的主机名，即使不是合法子域名，攻击者可通过控制其连接的反向DNS绕过基于主机的限制，可能导致未经授权的客户端修改。

CVSS 3.7 · Low EPSS 0.32% · P22

Affected Version Matrix 6

VendorProduct Version RangeStatus
Red Hat Red Hat Build of Keycloak any affected
any affected
any affected
Red Hat Red Hat Data Grid 8 any unaffected
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack any unaffected
Red Hat Red Hat Single Sign-On 7 any unaffected
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I. Basic Information for CVE-2026-18206

Vulnerability Information
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Vulnerability Title
Keycloak-services: keycloak-services: client policy source-host wildcard domain matching bypass
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Keycloak 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Keycloak是Keycloak组织开源的一种身份和访问管理解决方案。 Keycloak存在输入验证错误漏洞，该漏洞源于通配符域名的验证不当，系统接受任何以指定域名后缀结尾的主机名，即使不是合法子域名，攻击者可通过控制其连接的反向DNS绕过基于主机的限制，可能导致未经授权的客户端修改。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Red Hat Red Hat Build of Keycloak - cpe:/a:redhat:build_keycloak:
Red Hat Red Hat Build of Keycloak - cpe:/a:redhat:build_keycloak:
Red Hat Red Hat Build of Keycloak - cpe:/a:redhat:build_keycloak:
Red Hat Red Hat Data Grid 8 - cpe:/a:redhat:jboss_data_grid:8
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack - cpe:/a:redhat:jbosseapxp
Red Hat Red Hat Single Sign-On 7 - cpe:/a:redhat:red_hat_single_sign_on:7

II. Public POCs for CVE-2026-18206

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III. Intelligence Information for CVE-2026-18206

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Vendor Advisories for CVE-2026-18206 (2)

Same Patch Batch · Red Hat · 2026-07-31 · 14 CVEs total

CVE-2026-10079 8.5 HIGH Stackrox: stackrox: deploy-time policy enforcement and visibility bypass via label injecti
CVE-2026-18141 8.2 HIGH Aap-gateway: aap-gateway: authentication bypass in event-driven ansible via forged http he
CVE-2026-15722 7.5 HIGH 389-ds-base: 389-ds-base: pre-authentication stack buffer overflow in get_ruvelement_from_
CVE-2026-11770 7.5 HIGH 389-ds-base: 389-ds-base: pre-auth ldap filter injection in cleanallruv status check
CVE-2026-18215 6.8 MEDIUM Keycloak-services: keycloak-services: microsoft external access-token exchange bypasses co
CVE-2026-18214 6.8 MEDIUM Keycloak-services: keycloak-services: google external access-token exchange bypasses hoste
CVE-2026-18208 6.5 MEDIUM Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks s
CVE-2026-18203 6.5 MEDIUM Keycloak-services: keycloak-services: group policy extendchildren matches sibling group pa
CVE-2026-16105 4.9 MEDIUM Keycloak-services: keycloak-services: missing per-role authorization on rolecontainerresou
CVE-2026-18218 4.2 MEDIUM Keycloak-services: keycloak-services: client not-before revocation ignored when realm not-
CVE-2026-18211 4.2 MEDIUM Keycloak-services: keycloak-services: secure-client-uris policy bypass via localhost-prefi
CVE-2026-18217 3.4 LOW Keycloak-services: keycloak-services: saml http-redirect binding response preserves query
CVE-2026-18209 3.4 LOW Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter

IV. Related Vulnerabilities

Same product: Red Hat Build of Keycloak
Same vendor: Red Hat
Same weakness: CWE-20

V. Comments for CVE-2026-18206

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