# CVE-2026-4634

## Summary

- **CVE ID:** CVE-2026-4634
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-1050
- **Published:** Apr 2, 2026
- **Last Modified:** Jul 15, 2026

## Description

A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.

## Affected Products

- Red Hat — Red Hat build of Keycloak 26.2 (26.2.15-1)
- Red Hat — Red Hat build of Keycloak 26.2 (26.2-18)
- Red Hat — Red Hat build of Keycloak 26.4 (26.4.11-1)
- Red Hat — Red Hat build of Keycloak 26.4 (26.4-14)

## References

- [CNA](https://access.redhat.com/errata/RHSA-2026:6475)
- [CNA](https://access.redhat.com/errata/RHSA-2026:6476)
- [CNA](https://access.redhat.com/errata/RHSA-2026:6477)
- [CNA](https://access.redhat.com/errata/RHSA-2026:6478)
- [CNA](https://access.redhat.com/security/cve/CVE-2026-4634)
- [CNA](https://bugzilla.redhat.com/show_bug.cgi?id=2450250)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4634.json)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.52%
- **EPSS Percentile:** 42.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._