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KeycloakApplication · Redhat

CVE-2023-6563

HIGH · 7.7 CVSS v3.1 Published 2023-12-14
Fix available
A fix is available. Upgrade to 21.0.0 or later.
See remediation →
83/100
Remediation priority · High
Public exploit Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-770

The application allocates memory, connections, or handles in response to a request without enforcing any cap, so a modest amount of malicious traffic exhausts the resource and denies service to everyone else. The fix is enforcing quotas, limits, and timeouts on what any single request or client can consume.

General guidance for the resource allocation without limits class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
KeycloakApplication
Affected:< 21.0.0
Single Sign OnApplication
Affected:= 7.6all versions
Openshift Container PlatformApplication
Affected:= 4.11= 4.12
Openshift Container Platform For PowerApplication
Affected:= 4.9= 4.10
Openshift Container Platform For Ibm LinuxoneApplication
Affected:= 4.9= 4.10

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 21.0.0 or later
Fixed in 21.0.0
Recommended fix High confidence

Keycloak 21.0.0 or later; Red Hat security advisories for affected RH-SSO and OpenShift Container Platform versions

  1. Upgrade Keycloak to version 21.0.0 or later to resolve the unconstrained memory consumption vulnerability
  2. For Red Hat Single Sign-On (RH-SSO) deployments, apply the relevant security advisory update for version 7.6 or earlier
  3. For OpenShift Container Platform deployments, apply the Red Hat security updates for versions 4.11 and 4.12 that address this Keycloak vulnerability
  4. For OpenShift Container Platform for Power and IBM LinuxONE, apply the Red Hat security updates for versions 4.9 and 4.10
  5. After upgrading, verify that the admin UI 'consents' tab no longer causes excessive memory consumption when loading offline client sessions
Caveat Major version upgrades in Keycloak may introduce breaking changes; review Keycloak 21.0.0 release notes for migration considerations

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-6563 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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