CVE-2026-4634 — keycloak
CVE-2026-4634 is a CWE-1050 vulnerability in keycloak. A fix is available for keycloak — see the affected versions and patch details below.
Keycloak: keycloak: denial of service via excessive processing of openid connect scope parameters
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-4634.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
keycloakReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Bitnami packages — download data is not available via public APIs for these ecosystems.
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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦Bitnami | keycloak | ≥ 26.2.0&&< 26.2.1 | 26.2.1 |
Affected Products
build of keycloakredhatDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for keycloak, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update keycloak to 26.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4634 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This is an Important denial of service vulnerability in Red Hat Build of Keycloak (RHBK). An unauthenticated attacker can exploit this flaw by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect token endpoint, leading to high resource consumption and prolonged…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-4634 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat build of Keycloak 26.2 | rhbk/keycloak-operator-bundle:26.2.15-1 | RHSA-2026:6476 |
| Red Hat build of Keycloak 26.2.15 | rhbk/keycloak-rhel9 | RHSA-2026:6475 |
| Red Hat build of Keycloak 26.4 | rhbk/keycloak-operator-bundle:26.4.11-1 | RHSA-2026:6478 |
| Red Hat build of Keycloak 26.4.11 | rhbk/keycloak-rhel9 | RHSA-2026:6477 |
| Red Hat Single Sign-On 7.6.13 | keycloak-services | RHSA-2026:76132 |
| Red Hat Single Sign-On 7.6 for RHEL 7 | rh-sso7-keycloak-0:18.0.20-1.redhat_00001.1.el7sso | RHSA-2026:76128 |
| Red Hat Single Sign-On 7.6 for RHEL 8 | rh-sso7-keycloak-0:18.0.20-1.redhat_00001.1.el8sso | RHSA-2026:76129 |
| Red Hat Single Sign-On 7.6 for RHEL 9 | rh-sso7-keycloak-0:18.0.20-1.redhat_00001.1.el9sso | RHSA-2026:76130 |
Frequently Asked Questions
Is CVE-2026-4634 in your dependencies?
Find it across Bitnami, including transitive dependencies.