How severe is CVE-2021-4133?

CVE-2021-4133 has a CVSS 3.x base score of 8.8, 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 high.

Is CVE-2021-4133 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-4133?

CVE-2021-4133 affects Redhat Keycloak. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-4133?

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.

When was CVE-2021-4133 published?

CVE-2021-4133 was published on 2022-01-25 and last updated on 2026-06-17.

CVE-2021-4133

CVE-2021-4133 is a high-severity vulnerability in Redhat Keycloak with a CVSS 3.x base score of 8.8. 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-863.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 1% (68th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Redhat Keycloak
Published: 2022-01-25
Last modified: 2026-06-17

Description

A flaw was found in Keycloak in versions from 12.0.0 and before 15.1.1 which allows an attacker with any existing user account to create new default user accounts via the administrative REST API even when new user registration is disabled.

Frequently asked questions

What is CVE-2021-4133?: A flaw was found in Keycloak in versions from 12.0.0 and before 15.1.1 which allows an attacker with any existing user account to create new default user accounts via the administrative REST API even when new user registration is disabled.
How severe is CVE-2021-4133?: CVE-2021-4133 has a CVSS 3.x base score of 8.8, 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 high.
Is CVE-2021-4133 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-4133?: CVE-2021-4133 affects Redhat Keycloak. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-4133?: 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.
When was CVE-2021-4133 published?: CVE-2021-4133 was published on 2022-01-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:redhat:keycloak:*:*:*:*:*:*:*:*

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