CVE-2021-35472 in LemonLDAP::NG
Summary
by MITRE • 07/30/2021
An issue was discovered in LemonLDAP::NG before 2.0.12. Session cache corruption can lead to authorization bypass or spoofing. By running a loop that makes many authentication attempts, an attacker might alternately be authenticated as one of two different users.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/06/2021
The vulnerability identified as CVE-2021-35472 affects LemonLDAP::NG versions prior to 2.0.12 and represents a critical session management flaw that compromises the integrity of the authentication system. This issue stems from improper handling of session cache mechanisms within the web application firewall and identity management framework. The vulnerability manifests when the system experiences concurrent authentication requests that cause race conditions in session storage, leading to unpredictable user impersonation scenarios. The flaw specifically impacts the session cache implementation where multiple simultaneous authentication attempts can corrupt session data structures, creating opportunities for unauthorized access and privilege escalation.
The technical root cause of this vulnerability lies in the lack of proper synchronization mechanisms when handling concurrent session creation and modification operations. When multiple authentication requests are processed simultaneously, the session cache becomes corrupted due to insufficient locking mechanisms or atomic operations during session data updates. This creates a scenario where session identifiers may become associated with incorrect user contexts, allowing an attacker to exploit the race condition by repeatedly submitting authentication requests. The vulnerability operates at the application layer and specifically targets the session management subsystem, making it particularly dangerous as it can be leveraged to bypass authentication controls entirely.
From an operational perspective, this vulnerability presents significant risks to organizations relying on LemonLDAP::NG for access control and single sign-on functionality. The authorization bypass capability means that attackers can potentially gain access to resources and data that should be restricted to specific user groups or roles. The spoofing aspect allows for user impersonation attacks where an attacker might alternate between two different user accounts during the authentication process, effectively creating a man-in-the-middle scenario. This vulnerability can be exploited by automated tools that rapidly submit authentication requests, making it particularly dangerous in environments with high traffic volumes or where the system is under stress conditions.
The impact of CVE-2021-35472 aligns with CWE-362, which describes a race condition vulnerability in concurrent programming scenarios. This weakness specifically manifests in the session cache management code where multiple threads or processes attempt to modify shared session data without proper coordination. The vulnerability also maps to ATT&CK technique T1078.004 which covers valid accounts through compromised credentials, as the authentication bypass allows attackers to effectively impersonate legitimate users. Organizations using LemonLDAP::NG should immediately implement the vendor-provided patch version 2.0.12 which includes proper session cache synchronization mechanisms and atomic operations to prevent the race conditions that enable this exploitation. Additionally, implementing rate limiting and monitoring for unusual authentication patterns can help detect exploitation attempts, though the primary defense remains the software update to address the core session management flaw.
Security teams should conduct comprehensive vulnerability assessments to identify systems running affected versions of LemonLDAP::NG and prioritize immediate remediation. The vulnerability's exploitation potential increases when combined with other authentication-related weaknesses in the broader infrastructure, making layered security approaches essential for comprehensive protection. Organizations should also review their session management configurations and implement additional controls such as session timeout policies and secure session identifier generation to further reduce the attack surface. The patch implementation requires careful testing to ensure compatibility with existing authentication workflows and session handling mechanisms within the organization's infrastructure.