Keycloak: keycloak: access token disclosure and implicit flow bypass via forged client data
Summary
| CVE | CVE-2026-7571 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-19 12:16:19 UTC |
| Updated | 2026-06-03 19:41:25 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.1 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
EPSS: 0.000120000 probability, percentile 0.019570000 (date 2026-06-03)
Problem Types: CWE-472 | CWE-472 External Control of Assumed-Immutable Web Parameter
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 7.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N |
| 3.1 | CNA | CVSS | 7.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Redhat | Build Of Keycloak | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4.12-1 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-17 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4 | unaffected 26.4-17 * rpm | Not specified |
| CNA | Red Hat | Red Hat Build Of Keycloak 26.4.12 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:19596 | [email protected] | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:19597 | [email protected] | access.redhat.com | Vendor Advisory |
| access.redhat.com/security/cve/CVE-2026-7571 | [email protected] | access.redhat.com | Vendor Advisory |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Evan Hendra for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-04-30T22:22:41.973Z | Reported to Red Hat. |
| CNA | 2026-05-19T10:50:49.394Z | Made public. |
Workarounds
CNA: 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.