A flaw was found in the Keycloak server during refresh token processing, specifically in the TokenManager class responsible for enforcing refresh token reuse policies. When strict refresh token rotation is enabled, the validation and update of refresh token usage are not performed atomically. This allows concurrent refresh requests to bypass single-use enforcement and issue multiple access tokens from the same refresh token. As a result, Keycloak’s refresh token rotation hardening can be undermined.
This vulnerability has a CVSS score of 3.1, classifying it as low severity. Although the vulnerability is not currently being actively exploited, organizations should still be cautious, as the potential for risk exists due to the nature of the issue. Organizations should address this vulnerability in their priority patch cycle.
The risk to organizations includes the possibility of multiple access tokens being issued from a single refresh token, which can compromise the integrity of the authentication process. This could lead to unauthorized access if an attacker manages to exploit this flaw.
Organizations should prioritize patching immediately to mitigate the associated risks and ensure the security of their Keycloak implementations.
Vulnerability Details
The vulnerability allows for an atomicity flaw in the refresh token processing of the Keycloak server. The publication date for this vulnerability is January 21, 2026. The Common Weakness Enumeration (CWE) classification for this issue is CWE-367.
Technical Analysis
The root cause of the vulnerability stems from the concurrent handling of refresh token requests, which allows them to bypass the single-use enforcement mechanism. The attack vector is classified as network-based, and the attack complexity is high, requiring low privileges and no user interaction.
The integrity impact is low, as the flaw does not affect confidentiality or availability. The flaw's scope remains unchanged, meaning it does not affect the system's overall security posture but can lead to potential misuse of tokens.
Risk & Impact Analysis
Real-world risk from this vulnerability includes the possibility of unauthorized access through the misuse of issued access tokens. The blast radius potential of this vulnerability could compromise multiple user sessions if not addressed. Given the CVSS score and the current status of not being actively exploited, organizations should schedule remediation.
Organizations should assess the impact on their systems and patch or update to the latest version of Keycloak to mitigate this risk.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Currently, there are no specific affected versions listed. Organizations should ensure that they are running the latest patches provided by the vendor.
Mitigation & Remediation
Organizations should prioritize patching immediately. It is essential to regularly update the Keycloak server to the latest version to mitigate vulnerabilities. As an additional measure, organizations can perform security assessments to identify any potential weaknesses in their implementation.
For further guidance on security assessments, organizations can refer to our application security assessment services.
Detection Guidance
Monitoring logs for any abnormal behavior related to token issuance can help detect potential exploitation attempts. Organizations should also be aware of any unauthorized access patterns that may indicate misuse of refresh tokens.
AppSecure Threat Intelligence Insight
This vulnerability highlights the importance of robustness in token management systems. Security teams should take note of the patterns that emerge from such vulnerabilities to enhance their overall security posture.
For insights on securing token management systems, organizations are encouraged to explore our penetration testing methodology and vulnerability management program design services.
Moreover, the incident underscores the necessity for organizations to stay informed about emerging vulnerabilities. Following our ransomware targeting trends can provide valuable insights into risk management.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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