EUVD-2026-30888
GHSA-hq3p-w4xv-x7vp
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Primary rating from NVD.
CVSS VectorNVD
Lifecycle Timeline
1Blast Radius
ecosystem impact- 61 maven packages depend on org.keycloak:keycloak-services (28 direct, 33 indirect)
Ecosystem-wide dependent count for version 26.6.2.
DescriptionCVE.org
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.
AnalysisAI
Implicit flow bypass in Red Hat Build of Keycloak allows a low-privileged authenticated user who already knows another user's credentials and a client ID to obtain OIDC access tokens from clients where the implicit flow was explicitly disabled. Beyond the unauthorized token issuance, the resulting tokens can be written to server logs, proxy logs, and HTTP Referer headers, broadening the disclosure surface. No public exploit identified at time of analysis and the issue is not listed in CISA KEV.
Technical ContextAI
Keycloak is Red Hat's open-source identity and access management server implementing OpenID Connect, OAuth 2.0, and SAML. OIDC defines an 'implicit flow' in which tokens are returned directly in the redirect URI fragment rather than via the back-channel token endpoint; because this places bearer tokens into URLs (and therefore into browser history, Referer headers, and intermediary logs), administrators routinely disable it per OAuth 2.0 Security BCP guidance. The root cause is CWE-472 (External Control of Assumed-Immutable Web Parameter): during a session-restart code path, client configuration data the server should treat as authoritative is influenced by attacker-supplied input, so the 'implicit flow disabled' setting is not enforced. The affected component is identified in CPE data as cpe:2.3:a:red_hat:red_hat_build_of_keycloak (version range marked '*'), corresponding to the Red Hat Build of Keycloak distribution rather than upstream Keycloak specifically.
RemediationAI
Patch availability is not explicitly enumerated in the provided data, so this should be treated as: Patch available per vendor advisory - apply the fixed Red Hat Build of Keycloak release referenced at https://access.redhat.com/security/cve/CVE-2026-7571 once the exact errata version is confirmed via that page and https://bugzilla.redhat.com/show_bug.cgi?id=2464263. Until the fixed build is deployed, compensating controls include rotating any credentials for low-privilege users that could plausibly have been used to mint unintended tokens, scrubbing access tokens from web server and reverse-proxy access logs and disabling URL logging for OIDC redirect endpoints, stripping Referer headers at the egress proxy for the Keycloak hostname, and tightening client registration so untrusted users cannot enumerate or supply arbitrary client IDs; each of these reduces token leakage surface but does not block the underlying flow-bypass, and disabling Referer or URL logging can complicate incident forensics.
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Same technique Information Disclosure
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