CVE-2026-7571

Keycloak: keycloak: access token disclosure and implicit flow bypass via forged client data

Published May 19, 2026 CVSS 3.1 · 7.1 High EPSS < 1% KEV · Not listed
Description
A flaw was found in Keycloak. A low-privilege user, with knowledge of user credentials and client ID, can bypass a security control intended to disable the implicit flow in OpenID Connect (OIDC) clients. By manipulating client data during a session restart, an attacker can obtain an access token that should not be available. This vulnerability can also lead to the exposure of these access tokens in server logs, proxy logs, and HTTP Referrer headers, resulting in sensitive information disclosure.

Remediation

Vendor Workaround

To mitigate this issue, restrict network access to the Keycloak authentication endpoint to trusted clients and networks. Implement firewall rules to control inbound connections to the Keycloak service ports, thereby reducing the attack surface and limiting who can initiate authentication flows and potentially exploit the implicit flow bypass. If the Keycloak service is reloaded or restarted, ensure these network restrictions remain in effect.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-hq3p-w4xv-x7vp Keycloak: Access token disclosure and implicit flow bypass via forged client data
History
Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
CPEs cpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:*:*:*:*
Vendors & Products Redhat build Of Keycloak
Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.4::el9
References
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in Keycloak. A low-privilege user, with knowledge of user credentials and client ID, can bypass a security control intended to disable the implicit flow in OpenID Connect (OIDC) clients. By manipulating client data during a session restart, an attacker can obtain an access token that should not be available. This vulnerability can also lead to the exposure of these access tokens in server logs, proxy logs, and HTTP Referrer headers, resulting in sensitive information disclosure.
Title Keycloak: keycloak: access token disclosure and implicit flow bypass via forged client data
First Time appeared Redhat
Redhat build Keycloak
Weaknesses CWE-472
CPEs cpe:/a:redhat:build_keycloak:
Vendors & Products Redhat
Redhat build Keycloak
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
May 20, 2026, 4:08 PM
Reserved
Apr 30, 2026, 10:21 PM
Status
Analyzed
Published
May 19, 2026, 12:16 PM
Modified
Oct 26, 2026, 1:10 PM
Severity
Moderate
Public date
May 19, 2026, 10:50 AM