Log in Start free

Vulnerability · Published Apr 2, 2026 · Assigned by redhat

CVE-2026-4634Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters

High 7.5

In plain English

A high-severity security flaw in Red Hat build of Keycloak 26.2 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.6%top 49.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.keycloak:keycloak-services26.5.7GHSA-h4wv-g838-66g3

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat build of Keycloak 26.2 see references
Red Hat Red Hat build of Keycloak 26.2 see references
Red Hat Red Hat build of Keycloak 26.2 see references
Red Hat Red Hat build of Keycloak 26.2.15 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4.11 see references
Red Hat Red Hat Single Sign-On 7.6.13 see references
Red Hat Red Hat Single Sign-On 7.6 for RHEL 7 see references
Red Hat Red Hat Single Sign-On 7.6 for RHEL 8 see references
Red Hat Red Hat Single Sign-On 7.6 for RHEL 9 see references
Red Hat RHEL-8 based Middleware Containers see references

Weakness: CWE-1050 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References