CVE-2026-4634
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.
Scoring
- Severity
- HIGH
- CVSS base score
- 7.5
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS probability
- 0.52%
- CWE
- CWE-1050
- Published
- 2026-04-02
- Last modified
- 2026-07-15
Affected products
- Red Hat Red Hat build of Keycloak 26.2
- Red Hat Red Hat build of Keycloak 26.2
- Red Hat Red Hat build of Keycloak 26.4
- Red Hat Red Hat build of Keycloak 26.4
Weakness type
Related vulnerabilities
- CVE-2026-52681 — Sieve CPU resource usage is tracked in the compiled script, so an attacker that has valid...
- CVE-2026-71488 — league/commonmark: Quadratic-time denial of service when parsing crafted Markdown
- CVE-2026-22263 — Suricata http1: quadratic complexity in headers parsing over multiple packets
- CVE-2026-22261 — Suricata eve/alert: http1 xff handling can lead to denial of service
- CVE-2025-48866 — ModSecurity has possible DoS vulnerability in sanitiseArg action
- CVE-2025-47947 — ModSecurity Has Possible DoS Vulnerability
- CVE-2025-32907 — Libsoup: denial of service in server when client requests a large amount of overlapping ranges with range header
- CVE-2024-4068 — Memory Exhaustion in braces