CVE-2017-2646 in KeyCloak
Summary
by MITRE
It was found that when Keycloak before 2.5.5 receives a Logout request with a Extensions in the middle of the request, the SAMLSloRequestParser.parse() method ends in a infinite loop. An attacker could use this flaw to conduct denial of service attacks.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2017-2646 represents a critical denial of service flaw within Keycloak identity management software prior to version 2.5.5. This issue specifically manifests in the SAMLSloRequestParser.parse() method which processes Single Logout (SLO) requests within the Security Assertion Markup Language framework. The flaw occurs when a maliciously crafted Logout request contains Extensions elements positioned in the middle of the request structure, creating a condition that causes the parsing logic to enter an infinite loop state. This behavior fundamentally disrupts the normal processing flow of the authentication service, rendering it unresponsive to legitimate requests.
The technical implementation of this vulnerability stems from inadequate input validation and error handling within the SAML request parsing component. When the SAMLSloRequestParser encounters a Logout request with Extensions elements improperly positioned, the parser's internal state management fails to properly terminate the parsing cycle. This condition creates a recursive or iterative processing loop where the parser continuously processes the same request elements without advancing to the next logical step in the parsing sequence. The vulnerability aligns with CWE-835, which specifically addresses infinite loops in software implementations, and demonstrates how malformed input can be exploited to create resource exhaustion conditions.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire authentication infrastructure. An attacker capable of sending malicious Logout requests could systematically consume system resources through the infinite loop mechanism, leading to complete service unavailability for legitimate users. This denial of service condition affects not only individual authentication sessions but can potentially impact the broader authentication ecosystem, especially in environments where Keycloak serves as a central identity provider for multiple applications and services. The attack vector requires minimal privileges since it operates at the protocol parsing level rather than requiring authentication credentials.
Mitigation strategies for CVE-2017-2646 focus primarily on immediate software updates to Keycloak version 2.5.5 or later, which includes patched parsing logic that properly validates and handles malformed SAML requests. Organizations should also implement network-level protections such as rate limiting and request validation at the perimeter to detect and block suspicious Logout request patterns. Additionally, security monitoring should be enhanced to detect unusual processing patterns that might indicate an active exploitation attempt. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, and organizations should consider implementing defensive measures against such attack patterns in their security operations centers. The vulnerability highlights the importance of robust input validation and proper error handling in security-critical components, particularly those dealing with standardized protocol implementations like SAML.