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Keycloak: Privilege escalation via forged authorization codes due to SingleUseObjectProvider isolation flaw

High severity GitHub Reviewed Published Apr 2, 2026 to the GitHub Advisory Database • Updated Apr 4, 2026

Package

maven org.keycloak:keycloak-services (Maven)

Affected versions

< 26.5.7

Patched versions

26.5.7

Description

A flaw was found in Keycloak. The SingleUseObjectProvider, a global key-value store, lacks proper type and namespace isolation. This vulnerability allows an unauthenticated attacker to forge authorization codes. Successful exploitation can lead to the creation of admin-capable access tokens, resulting in privilege escalation.

References

Published by the National Vulnerability Database Apr 2, 2026
Published to the GitHub Advisory Database Apr 2, 2026
Reviewed Apr 4, 2026
Last updated Apr 4, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(10th percentile)

Weaknesses

Improper Isolation or Compartmentalization

The product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions. Learn more on MITRE.

CVE ID

CVE-2026-4282

GHSA ID

GHSA-hj93-h7pg-fh6v

Source code

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