How severe is CVE-2026-4636?

CVE-2026-4636 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-4636 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-4636?

CVE-2026-4636 primarily affects Redhat Build Of Keycloak. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-4636?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-4636 have an EU (EUVD) identifier?

Yes. CVE-2026-4636 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18213.

When was CVE-2026-4636 published?

CVE-2026-4636 was published on 2026-04-02 and last updated on 2026-06-30.

CVE-2026-4636

CVE-2026-4636 is a high-severity vulnerability in Redhat Build Of Keycloak with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-551.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18213
Weakness: CWE-551
Affected product: Redhat Build Of Keycloak
Published: 2026-04-02
Last modified: 2026-06-30

Description

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.

Frequently asked questions

What is CVE-2026-4636?: 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.
How severe is CVE-2026-4636?: CVE-2026-4636 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-4636 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-4636?: CVE-2026-4636 primarily affects Redhat Build Of Keycloak. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-4636?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-4636 have an EU (EUVD) identifier?: Yes. CVE-2026-4636 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18213.
When was CVE-2026-4636 published?: CVE-2026-4636 was published on 2026-04-02 and last updated on 2026-06-30.

References

Affected products (5)

cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:text-only:*:*:*
cpe:2.3:a:redhat:build_of_keycloak:26.2:*:*:*:text-only:*:*:*
cpe:2.3:a:redhat:build_of_keycloak:26.2.15:*:*:*:text-only:*:*:*
cpe:2.3:a:redhat:build_of_keycloak:26.4:*:*:*:text-only:*:*:*
cpe:2.3:a:redhat:build_of_keycloak:26.4.11:*:*:*:text-only:*:*:*

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