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CVE-2026-18203— Keycloak-services: keycloak-services: group policy extendchildren matches sibling group path prefixes

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存在授权问题漏洞，该漏洞源于组策略评估逻辑错误，使用简单的文本前缀检查验证组成员身份，可能允许属于具有相似起始名称的不同组的用户绕过安全检查，未经授权访问管理功能或受保护资源。

CVSS 6.5 · Medium EPSS 0.31% · P24 Updated Aug 31, 2026

Possible ATT&CK Techniques 1 AI

T1078.004 · Cloud Accounts

Affected Version Matrix 6

Vendor	Product	Version Range	Status
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-2026-18203

Vulnerability Information

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Vulnerability Title

Keycloak-services: keycloak-services: group policy extendchildren matches sibling group path prefixes

Source: CVE Program / CVE List V5

Vulnerability Description

A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Source: CVE Program / CVE List V5

Vulnerability Type

授权机制不正确

Source: CVE Program / CVE List V5

Vulnerability Title

Keycloak 授权问题漏洞

Source: CNNVD (China National Vulnerability Database)

Vulnerability Description

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
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-2026-18203

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-18203

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Vendor Advisories for CVE-2026-18203 (2)

🔗 cve-details vdb-entry x_refsource_REDHAT
🔗 2508291 – (CVE-2026-18203) CVE-2026-18203 keycloak-services: keycloak-services: Group policy extendChildren matches sibling group path prefixes issue-tracking x_refsource_REDHAT

https://www.cve.org/CVERecord?id=CVE-2026-18203

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-2026-16105	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-2026-18206	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-863