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CVE-2026-9087— Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login

Quick assessment

Affected
Red Hat Red Hat build of Keycloak 26.4
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，该漏洞源于跨会话验证证明仅基于本地用户ID和IdP别名，未绑定实际验证的上游身份，可能导致同一IdP上的第二个上游账户链接到受害者本地账户。

CVSS 6.4 · Medium EPSS 0.31% · P23

Affected Version Matrix 8

VendorProduct Version RangeStatus
Red Hat Red Hat build of Keycloak 26.4 26.4.13-1< * unaffected
26.4-19< * unaffected
26.4-19< * unaffected
Red Hat Red Hat build of Keycloak 26.4.13 any unaffected
Red Hat Red Hat build of Keycloak 26.6 26.6.3-3< * unaffected
26.6-6< * unaffected
26.6-6< * unaffected
Red Hat Red Hat build of Keycloak 26.6.3 any unaffected
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I. Basic Information for CVE-2026-9087

Vulnerability Information
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Vulnerability Title
Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login
Source: CVE Program / CVE List V5
Vulnerability Description
A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId, idpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume it and get linked to the victim's local account.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
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，该漏洞源于跨会话验证证明仅基于本地用户ID和IdP别名，未绑定实际验证的上游身份，可能导致同一IdP上的第二个上游账户链接到受害者本地账户。
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 26.4 26.4.13-1 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4 26.4-19 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4 26.4-19 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4.13 - cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.6 26.6.3-3 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-6 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-6 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.3 - cpe:/a:redhat:build_keycloak:26.6::el9

II. Public POCs for CVE-2026-9087

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III. Intelligence Information for CVE-2026-9087

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Vendor Advisories for CVE-2026-9087 (4)

Other References for CVE-2026-9087 (2)

Same Patch Batch · Red Hat · 2026-05-20 · 3 CVEs total

CVE-2026-9149 6.5 MEDIUM Libsolv: heap buffer overflow in libsolv repo_add_solv via negative maxsize from crafted .
CVE-2026-9150 6.5 MEDIUM Libsolv: stack-based buffer overflow in libsolv's debian metadata parser when handling sha

IV. Related Vulnerabilities

Same product: Red Hat build of Keycloak 26.4
Same vendor: Red Hat
Same weakness: CWE-639

V. Comments for CVE-2026-9087

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