CWE-551
Incorrect Behavior Order: Authorization Before Parsing and Canonicalization
If a web server does not fully parse requested URLs before it examines them for authorization, it may be possible for an attacker to bypass authorization protection.
CVE-2026-4636 (GCVE-0-2026-4636)
Vulnerability from cvelistv5 – Published: 2026-04-02 12:45 – Updated: 2026-06-09 13:56
VLAI
Title
Keycloak: keycloak: uma policy bypass allows authenticated users to gain unauthorized access to victim-owned resources.
Summary
A flaw was found in Keycloak. An authenticated user with the uma_protection role can bypass User-Managed Access (UMA) policy validation. This allows the attacker to include resource identifiers owned by other users in a policy creation request, even if the URL path specifies an attacker-owned resource. Consequently, the attacker gains unauthorized permissions to victim-owned resources, enabling them to obtain a Requesting Party Token (RPT) and access sensitive information or perform unauthorized actions.
Severity
8.1 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
- CWE-551 - Incorrect Behavior Order: Authorization Before Parsing and Canonicalization
Assigner
References
6 references
| URL | Tags |
|---|---|
| https://access.redhat.com/errata/RHSA-2026:6475 | vendor-advisoryx_refsource_REDHAT |
| https://access.redhat.com/errata/RHSA-2026:6476 | vendor-advisoryx_refsource_REDHAT |
| https://access.redhat.com/errata/RHSA-2026:6477 | vendor-advisoryx_refsource_REDHAT |
| https://access.redhat.com/errata/RHSA-2026:6478 | vendor-advisoryx_refsource_REDHAT |
| https://access.redhat.com/security/cve/CVE-2026-4636 | vdb-entryx_refsource_REDHAT |
| https://bugzilla.redhat.com/show_bug.cgi?id=2450251 | issue-trackingx_refsource_REDHAT |
Impacted products
6 products
| Vendor | Product | Version | |
|---|---|---|---|
| Red Hat | Red Hat build of Keycloak 26.2 |
Unaffected:
26.2.15-1 , < *
(rpm)
cpe:/a:redhat:build_keycloak:26.2::el9 |
|
| Red Hat | Red Hat build of Keycloak 26.2 |
Unaffected:
26.2-18 , < *
(rpm)
cpe:/a:redhat:build_keycloak:26.2::el9 |
|
| Red Hat | Red Hat build of Keycloak 26.2.15 |
cpe:/a:redhat:build_keycloak:26.2::el9 |
|
| Red Hat | Red Hat build of Keycloak 26.4 |
Unaffected:
26.4.11-1 , < *
(rpm)
cpe:/a:redhat:build_keycloak:26.4::el9 |
|
| Red Hat | Red Hat build of Keycloak 26.4 |
Unaffected:
26.4-14 , < *
(rpm)
cpe:/a:redhat:build_keycloak:26.4::el9 |
|
| Red Hat | Red Hat build of Keycloak 26.4.11 |
cpe:/a:redhat:build_keycloak:26.4::el9 |
Date Public
2026-04-02 12:30
Credits
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Mitigation
Phase: Architecture and Design
Description:
- URL Inputs should be decoded and canonicalized to the application's current internal representation before being validated and processed for authorization. Make sure that your application does not decode the same input twice. Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked.
No CAPEC attack patterns related to this CWE.