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CVE-2026-18211— Keycloak-services: keycloak-services: secure-client-uris policy bypass via localhost-prefixed domains

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secure-client-uris客户端策略执行器对web地址仅检查开头而未正确验证主机，可能导致攻击者利用特制域名绕过安全限制，拦截敏感认证码。

CVSS 4.2 · Medium EPSS 0.31% · P24

Possible ATT&CK Techniques 1 AI

T1562.001

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-2026-18211

Vulnerability Information
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Vulnerability Title
Keycloak-services: keycloak-services: secure-client-uris policy bypass via localhost-prefixed domains
Source: CVE Program / CVE List V5
Vulnerability Description
A flaw was found in the secure-client-uris client policy executor within Keycloak core services. This component is responsible for enforcing security requirements on client configurations, such as requiring encrypted connections for redirect URIs. Due to an improper check that only looks at the start of a web address rather than properly verifying the host, an attacker can bypass these security restrictions by using a specially crafted domain name. This could allow an attacker to intercept sensitive authentication codes over unencrypted connections.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/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secure-client-uris客户端策略执行器对web地址仅检查开头而未正确验证主机，可能导致攻击者利用特制域名绕过安全限制，拦截敏感认证码。
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-2026-18211

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III. Intelligence Information for CVE-2026-18211

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Vendor Advisories for CVE-2026-18211 (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-2026-18206 3.7 LOW Keycloak-services: keycloak-services: client policy source-host wildcard domain matching b
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