What is CVE-2021-3637?

CVE-2021-3637 is a high-severity vulnerability in Red Hat Keycloak, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2021-07-09.

How severe is CVE-2021-3637?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Red Hat Keycloak

CVE-2021-3637

A flaw was found in keycloak-model-infinispan in keycloak versions before 14.0.0 where authenticationSessions map in RootAuthenticationSessionEntity grows boundlessly which could lead to a DoS attack.

Published 2021-07-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.011 (65.2th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 65.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

Red Hat Keycloak
Red Hat Single Sign-On — versions 7.0
Keycloak-Model-Infinispan — versions keycloak 14.0.0

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

bugzilla.redhat.com/show_bug.cgi (Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2021-3637?: CVE-2021-3637 is a high-severity vulnerability in Red Hat Keycloak, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2021-07-09.
How severe is CVE-2021-3637?: High severity. CVSS v3 base score is 7.5 out of 10.