CVE-2026-4634

Summary

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 Software

VendorProductVersion RangeStatus
Red HatRed Hat build of Keycloak 26.226.2.15-1 < *unaffected
Red HatRed Hat build of Keycloak 26.226.2-18 < *unaffected
Red HatRed Hat build of Keycloak 26.226.2-18 < *unaffected
Red HatRed Hat build of Keycloak 26.426.4.11-1 < *unaffected
Red HatRed Hat build of Keycloak 26.426.4-14 < *unaffected
Red HatRed Hat build of Keycloak 26.426.4-14 < *unaffected

Weaknesses

  • CWE-1050: Excessive Platform Resource Consumption within a Loop

Workarounds

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.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

keycloak: Keycloak: Denial of Service via excessive processing of OpenID Connect scope parameters

Additional References

References