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7.7High

Redhat Keycloak

CVE-2023-6563

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

What this means for your business

  • It affects Redhat Keycloak. It matters if your company, or a supplier that handles your data, runs it.
  • Code showing how to exploit it has been published, but real attacks have not been confirmed.
  • An attacker can use it remotely, over a network, with an ordinary user login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 1% chance of attack attempts being seen in the next 30 days, ranking above 67% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Redhat Keycloak, and which version. The affected versions are listed further down this page.
  2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Check if you’re exposedBook a call

Scoring

CVSS
7.7 (v3.1)
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-770
Assigned by
secalert@redhat.com

Dates

Published
2023-12-14
Last modified
2026-09-22
Sources
NVD

Affected products

  • Redhat Keycloak- 21.0.0
  • Redhat Single Sign-On7.6, all versions
  • Redhat Enterprise Linux7.0, 8.0, 9.0
  • Redhat Openshift Container Platform4.11, 4.12
  • Redhat Openshift Container Platform For Power4.9, 4.10
  • Redhat Openshift Container Platform For Ibm Linuxone4.9, 4.10

As listed in the NVD configuration data. Not a statement about your estate.

References