CVE-2026-9704— Keycloak: keycloak: privilege escalation due to oversized subject_token jwt
Possible ATT&CK Techniques 1AI
T1078 · Valid AccountsAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Red Hat | Red Hat Build of Keycloak | any | affected |
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I. Basic Information for CVE-2026-9704
Vulnerability Information
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Vulnerability Title
Keycloak: keycloak: privilege escalation due to oversized subject_token jwt
Source: NVD (National Vulnerability Database)
Vulnerability Description
A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
CWE-1284
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，该漏洞源于经过身份验证的低权限用户可通过向TokenEndpoint发送过大的subject_token JWT令牌，当令牌超过4000字符限制时被静默丢弃，系统回退到客户端凭据，导致用户获得客户端服务账户的权限，实现权限提升。
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 | - | cpe:/a:redhat:build_keycloak: |
II. Public POCs for CVE-2026-9704
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|---|
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Vendor Advisories for CVE-2026-9704 (1)
- 🔗 2481877 – (CVE-2026-9704) CVE-2026-9704 keycloak: Keycloak: Privilege escalation due to oversized subject_token JWT Read full article issue-trackingx_refsource_REDHAT
Other References for CVE-2026-9704 (1)
Same Patch Batch · Red Hat · 2026-05-27 · 5 CVEs total
| CVE-2026-3012 | 8.0 HIGH | Samba: group policy certificate enrollment uses http:// without validation |
| CVE-2026-1933 | 7.1 HIGH | Samba: missing access check on reparse point operations |
| CVE-2026-2340 | 6.5 MEDIUM | Samba: vfs_worm does not block directory modification |
| CVE-2026-9689 | 4.2 MEDIUM | Keycloak: org.keycloak.protocol.oidc: http parameter pollution in oidc redirect uri allows |
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V. Comments for CVE-2026-9704
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