CVE-2006-5779 in OpenLDAP
Summary
by MITRE
OpenLDAP before 2.3.29 allows remote attackers to cause a denial of service (daemon crash) via LDAP BIND requests with long authcid names, which triggers an assertion failure.
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Analysis
by VulDB Data Team • 04/26/2026
OpenLDAP version 2.3.29 and earlier contains a critical denial of service vulnerability that can be exploited by remote attackers through carefully crafted LDAP BIND requests. This vulnerability specifically targets the authentication process where the daemon encounters malformed authcid names that exceed expected length parameters, leading to an assertion failure that crashes the entire service. The flaw exists in the LDAP protocol handling mechanism where the software fails to properly validate input lengths during the authentication phase, creating a condition where excessive data can trigger internal assertion checks that were not designed to handle such scenarios. This vulnerability falls under the category of improper input validation and can be classified as a CWE-122 (Heap-based Buffer Overflow) or CWE-787 (Out-of-bounds Write) depending on the specific implementation details, and it aligns with ATT&CK technique T1499.004 (Endpoint Denial of Service) in its operational impact. The daemon crash occurs when the LDAP server processes a BIND request containing an authentication identity (authcid) that exceeds the maximum allowable length, causing the software to assert that a condition has failed and terminate the service. This behavior represents a fundamental flaw in the input sanitization process where the system does not properly handle edge cases or oversized inputs, particularly within the authentication context. The vulnerability is particularly concerning because it allows an unauthenticated attacker to remotely disrupt service availability without requiring any special privileges or credentials. The attack vector is straightforward as it only requires sending a malformed LDAP BIND request with an excessively long authcid field to the target OpenLDAP server. This denial of service condition affects all versions prior to 2.3.29 and can be exploited across different network configurations where OpenLDAP services are exposed to external traffic. Organizations running vulnerable versions of OpenLDAP are at risk of experiencing service interruptions that can impact directory services, authentication systems, and applications that depend on LDAP for user management and access control. The operational impact extends beyond simple service disruption as it can affect enterprise authentication infrastructure, potentially causing cascading failures in systems that rely on directory services for user provisioning and access management. The vulnerability demonstrates a lack of proper bounds checking in the LDAP processing pipeline, where the system fails to implement adequate input length validation before processing authentication requests. This flaw is particularly dangerous in environments where OpenLDAP serves as a core authentication service, as a successful attack can render the entire directory service unavailable. The fix for this vulnerability required implementing proper input validation and length checking mechanisms within the LDAP BIND processing code, ensuring that authcid values are properly bounded before being processed by the assertion checks. Organizations should prioritize upgrading to OpenLDAP version 2.3.29 or later to mitigate this risk, as the patch addresses the root cause by implementing proper input sanitization and preventing the assertion failure condition. System administrators should also consider implementing network-level protections such as rate limiting and input filtering to reduce the exposure window while applying the necessary software updates. The vulnerability highlights the importance of robust input validation in network services and demonstrates how seemingly benign protocol features can become attack vectors when proper boundary checking is not implemented. This issue serves as a reminder of the critical need for comprehensive testing of edge cases in authentication protocols and the potential for denial of service attacks to be triggered through protocol-specific input handling flaws. The attack scenario can be easily automated and does not require specialized tools or knowledge of the underlying system architecture, making it particularly dangerous for widespread exploitation in unpatched environments.