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CVE-2026-11800— Org.keycloak:keycloak-services: keycloak: authentication bypass via jwt algorithm confusion

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组织开源的一种开源身份和访问管理解决方案。 Keycloak存在加密问题漏洞，该漏洞源于JWT Authorization Grant流程中的JWT算法混淆，允许拥有有效客户端凭据的攻击者绕过签名验证。通过伪造断言，攻击者可以创建未经授权的访问令牌，从而冒充受影响身份提供者关联的任何联邦用户，导致未经授权的访问和潜在权限提升。

CVSS 8.1 · High EPSS 0.30% · P21

Affected Version Matrix 9

VendorProduct Version RangeStatus
Red Hat Red Hat Build of Keycloak any affected
any unaffected
Red Hat Red Hat build of Keycloak 26.6 26.6.4-2< * unaffected
26.6-8< * unaffected
26.6-8< * unaffected
Red Hat Red Hat build of Keycloak 26.6.4 any unaffected
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-2026-11800

Vulnerability Information
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Vulnerability Title
Org.keycloak:keycloak-services: keycloak: authentication bypass via jwt algorithm confusion
Source: CVE Program / CVE List V5
Vulnerability Description
A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Keycloak 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Keycloak是Keycloak组织开源的一种开源身份和访问管理解决方案。 Keycloak存在加密问题漏洞，该漏洞源于JWT Authorization Grant流程中的JWT算法混淆，允许拥有有效客户端凭据的攻击者绕过签名验证。通过伪造断言，攻击者可以创建未经授权的访问令牌，从而冒充受影响身份提供者关联的任何联邦用户，导致未经授权的访问和潜在权限提升。
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 26.6.4-2 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-8 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-8 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.4 - cpe:/a:redhat:build_keycloak:26.6::el9
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-2026-11800

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III. Intelligence Information for CVE-2026-11800

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Vendor Advisories for CVE-2026-11800 (1)

Other References for CVE-2026-11800 (3)

Same Patch Batch · Red Hat · 2026-06-25 · 13 CVEs total

CVE-2026-12975 8.5 HIGH Apicurio/apicurio-registry: apicurio-registry: unhardened saxparser in content-type detect
CVE-2026-9800 8.1 HIGH Keycloak-policy-enforcer: keycloak policy enforcer: authorization bypass via incorrect uri
CVE-2026-9099 7.7 HIGH Keycloak: group-admin escalation to realm-admin
CVE-2026-12992 7.4 HIGH Apicurio/apicurio-registry: apicurio-registry: ssrf via wsdl4j import dereference in wsdl
CVE-2026-9086 7.3 HIGH Keycloak: keycloak: cross-site scripting (xss) via case-insensitive uri validation bypass
CVE-2026-13083 6.9 MEDIUM Pen-drive: pen-drive: stored xss via unescaped cluster data in html report
CVE-2026-9705 6.5 MEDIUM Keycloak: keycloak: attacker can re-enable and take over disabled clients via registration
CVE-2026-12993 6.5 MEDIUM Apicurio/apicurio-registry: apicurio-registry: xml entity-expansion denial of service via
CVE-2026-13318 6.4 MEDIUM Virt-api-rhel9: kubevirt: kubevirt: ssrf in virt-api port-forward via unvalidated guest-ag
CVE-2026-9083 4.9 MEDIUM Keycloak: keycloak: information disclosure through arbitrary filesystem path probing
CVE-2026-9799 4.6 MEDIUM Keycloak: keycloak: unauthorized access to resources via uma permission ticket bypass
CVE-2026-13218 4.2 MEDIUM Kubevirt: kubevirt: symlink following in writetocachedfile allows host file overwrite from

IV. Related Vulnerabilities

Same product: Red Hat build of Keycloak 26.6
Same vendor: Red Hat
Same weakness: CWE-347

V. Comments for CVE-2026-11800

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