CVE-2016-0741 in 389 Directory Server
Summary
by MITRE
slapd/connection.c in 389 Directory Server (formerly Fedora Directory Server) 1.3.4.x before 1.3.4.7 allows remote attackers to cause a denial of service (infinite loop and connection blocking) by leveraging an abnormally closed connection.
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Analysis
by VulDB Data Team • 07/25/2022
The vulnerability identified as CVE-2016-0741 affects the 389 Directory Server implementation of the slapd daemon, specifically within the connection.c module. This directory server implementation is widely used for storing and managing directory information services in enterprise environments, serving as a critical component for authentication and authorization systems. The flaw manifests in the handling of connection states when clients abruptly close their connections without proper termination sequences, creating a scenario where the server enters an infinite loop while attempting to process these malformed connection closures.
The technical root cause of this vulnerability lies in the improper state management within the slapd connection handling logic. When a client establishes a connection to the directory server and then closes it abruptly without following the standard LDAP protocol termination procedures, the server's connection.c module fails to properly validate or handle this abnormal closure condition. This results in the server entering a continuous loop attempting to process the connection state, effectively blocking the connection and preventing legitimate client requests from being serviced. The infinite loop consumes system resources and renders the directory service unavailable to other users, creating a classic denial of service condition.
From an operational perspective, this vulnerability presents a significant risk to directory service availability, particularly in environments where 389 Directory Server serves as a foundational component for identity management and authentication. Attackers can exploit this flaw by establishing connections to the server and then abruptly closing them, causing the server to become unresponsive and effectively denying service to legitimate users. The impact extends beyond simple availability issues as the infinite loop can consume substantial CPU resources and memory, potentially leading to system instability or crashes. Organizations relying on LDAP-based authentication systems may experience cascading failures as dependent services lose access to critical directory information.
The vulnerability aligns with CWE-835, which specifically addresses infinite loops in software implementations, and can be categorized under the ATT&CK technique T1499.004 for Network Denial of Service. Organizations should implement immediate mitigations including applying the vendor-provided patches that address the connection handling logic in slapd, configuring connection timeouts to prevent indefinite hanging states, and implementing monitoring solutions to detect unusual connection patterns that may indicate exploitation attempts. Network segmentation and rate limiting controls can also help reduce the impact of such attacks by limiting the number of concurrent connections and preventing rapid exploitation of the vulnerability. Additionally, regular security assessments and penetration testing should be conducted to identify similar state management issues in other directory services and network applications that may be susceptible to similar denial of service conditions.