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CVE-2026-4634— Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters

CVSS 7.5 · High EPSS 0.08% · P23
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I. Basic Information for CVE-2026-4634

Vulnerability Information
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Vulnerability Title
Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters
Source: NVD (National Vulnerability Database)
Vulnerability Description
A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
循环内过多的平台资源消耗
Source: NVD (National Vulnerability Database)
Vulnerability Title
Keycloak 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Keycloak是Keycloak开源的一种开源身份和访问管理解决方案。 Keycloak存在安全漏洞，该漏洞源于向OIDC令牌端点发送特制的超长scope参数POST请求，可能导致资源消耗过高和处理时间延长，最终造成拒绝服务。
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

VendorProductAffected VersionsCPESubscribe
Red HatRed Hat build of Keycloak 26.2 26.2.15-1 ~ * cpe:/a:redhat:build_keycloak:26.2::el9
Red HatRed Hat build of Keycloak 26.2 26.2-18 ~ * cpe:/a:redhat:build_keycloak:26.2::el9
Red HatRed Hat build of Keycloak 26.2 26.2-18 ~ * cpe:/a:redhat:build_keycloak:26.2::el9
Red HatRed Hat build of Keycloak 26.2.15-cpe:/a:redhat:build_keycloak:26.2::el9
Red HatRed Hat build of Keycloak 26.4 26.4.11-1 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red HatRed Hat build of Keycloak 26.4 26.4-14 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red HatRed Hat build of Keycloak 26.4 26.4-14 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red HatRed Hat build of Keycloak 26.4.11-cpe:/a:redhat:build_keycloak:26.4::el9

II. Public POCs for CVE-2026-4634

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III. Intelligence Information for CVE-2026-4634

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Same Patch Batch · Red Hat · 2026-04-02 · 5 CVEs total

CVE-2026-46368.1 HIGHKeycloak: keycloak: uma policy bypass allows authenticated users to gain unauthorized acce
CVE-2026-42827.4 HIGHKeycloak: keycloak: privilege escalation via forged authorization codes due to singleuseob
CVE-2026-38727.3 HIGHKeycloak: keycloak: information disclosure due to redirect_uri validation bypass
CVE-2026-43255.3 MEDIUMKeycloak: keycloak: replay of action tokens via improper handling of single-use entries

IV. Related Vulnerabilities

Same product: Red Hat build of Keycloak 26.2
Same vendor: Red Hat
Same weakness: CWE-1050

V. Comments for CVE-2026-4634

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