CVE-2017-2646: Keycloak vulnerable to infinite loop based Denial of Service
Summary
CVE-2017-2646: Keycloak vulnerable to infinite loop based Denial of Service. Affects org.keycloak:keycloak-core versions < 2.5.5. Fixed in 2.5.5. How to fix ↓
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Background
Keycloak is an open-source identity and access management solution that provides single sign-on capabilities for web applications and services. It is widely used to secure user authentication and authorization in various systems. The keycloak-core package is a core component of Keycloak that handles key functionalities and security features. However, versions prior to 2.5.5 of Keycloak are susceptible to an infinite loop-based Denial of Service (DoS) vulnerability.
Vulnerability Detail
The vulnerability in Keycloak arises when it receives a Logout request with an Extensions in the middle of the request. The SAMLSloRequestParser.parse() method, which is responsible for parsing the request, enters an infinite loop. This flaw can be exploited by an attacker to launch DoS attacks against the Keycloak server. By sending specially crafted Logout requests with Extensions, the server can be overwhelmed, leading to service disruption. The vulnerability has a CVSS score of 7.5, indicating a high severity level.
How To Fix
Latest published version: 26.8.1 as of 22 Oct 2026
Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
2.5.5
This is the first release that contains the fix.
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Workaround
There is no known workaround for this vulnerability. It is essential to apply the recommended fix by upgrading Keycloak to a secure version.
Conclusion
Keycloak versions prior to 2.5.5 are vulnerable to an infinite loop-based Denial of Service (DoS) attack. By sending specially crafted Logout requests with Extensions, an attacker can cause the Keycloak server to enter an infinite loop, leading to service disruption. To mitigate this vulnerability, it is crucial to upgrade Keycloak to version 2.5.5 or later. For further support on vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for org.keycloak:keycloak-core →
FAQ
Keycloak is an open-source identity and access management solution that provides single sign-on capabilities for web applications and services.
The vulnerability allows an attacker to launch DoS attacks against the Keycloak server, potentially leading to service disruption.
To fix this vulnerability, upgrade Keycloak to version 2.5.5 or later.
No, there is no known workaround for this vulnerability. Upgrading to a secure version is the recommended solution.
The CVSS score of this vulnerability is 7.5, indicating a high severity level.
Related vulnerabilities
Recent vulnerabilities recorded for org.keycloak:keycloak-core.
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