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CVE-2026-16093— Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers

Quick assessment

Affected
Red Hat Red Hat build of Keycloak 26.6
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，该漏洞源于客户端策略实施绕过问题，可能导致具有有效客户端凭据的攻击者通过提供伪造的未签名断言标头，使用更简单的方法（如客户端密钥）进行身份验证。

CVSS 5.4 · Medium EPSS 0.39% · P31

Possible ATT&CK Techniques 1 AI

T1199 · Trusted Relationship

Affected Version Matrix 9

VendorProduct Version RangeStatus
Red Hat Red Hat build of Keycloak 26.6 26.6.7-3< * unaffected
26.6-20< * unaffected
26.6-20< * unaffected
Red Hat Red Hat build of Keycloak 26.6.7 any unaffected
any unaffected
any unaffected
Red Hat Red Hat Data Grid 8 any affected
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack any affected
Red Hat Red Hat Single Sign-On 7 any affected
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I. Basic Information for CVE-2026-16093

Vulnerability Information
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Vulnerability Title
Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers
Source: CVE Program / CVE List V5
Vulnerability Description
Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在安全决策中依赖未经信任的输入
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，该漏洞源于客户端策略实施绕过问题，可能导致具有有效客户端凭据的攻击者通过提供伪造的未签名断言标头，使用更简单的方法（如客户端密钥）进行身份验证。
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 26.6 26.6.7-3 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-20 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-20 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
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-2026-16093

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III. Intelligence Information for CVE-2026-16093

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Vendor Advisories for CVE-2026-16093 (4)

Same Patch Batch · Red Hat · 2026-07-17 · 8 CVEs total

CVE-2026-15943 5.5 MEDIUM Keycloak-services: keycloak-services: oidc idp update reuses masked client secret after to
CVE-2026-16089 5.4 MEDIUM Keycloak-services: keycloak-services: authorization codes can be retargeted to another cli
CVE-2026-16106 4.9 MEDIUM Keycloak-services: keycloak-services: incorrect authorization in admin role-composite dele
CVE-2026-16072 4.9 MEDIUM Keycloak-services: keycloak-services: organization invitation link exposure allows unautho
CVE-2026-16104 4.3 MEDIUM Keycloak-services: keycloak-services: authenticator config endpoint exposes raw recaptcha
CVE-2026-16103 4.3 MEDIUM Keycloak-services: keycloak-services: incomplete fix for ciba brute-force lockout bypass a
CVE-2026-16108 4.3 MEDIUM Keycloak-services: keycloak-services: realm default-group reads disclose hidden groups und

IV. Related Vulnerabilities

Same product: Red Hat build of Keycloak 26.6
Same vendor: Red Hat
Same weakness: CWE-807

V. Comments for CVE-2026-16093

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