CVE-2006-0453 in Fedora Core
Summary
by MITRE
The LDAP component in Fedora Directory Server 1.0 allow remote attackers to cause a denial of service (crash) via a certain "bad BER sequence" that results in a free of uninitialized memory, as demonstrated using the ProtoVer LDAP test suite.
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Analysis
by VulDB Data Team • 08/03/2017
The vulnerability identified as CVE-2006-0453 affects the Lightweight Directory Access Protocol implementation within Fedora Directory Server version 1.0, representing a critical denial of service weakness that can be exploited remotely. This issue stems from inadequate input validation mechanisms within the LDAP processing component, specifically when handling malformed binary encoding representations. The flaw manifests when the server encounters a particular bad BER (Basic Encoding Rules) sequence during LDAP operations, leading to unpredictable system behavior and eventual service interruption. The vulnerability was demonstrated through the ProtoVer LDAP test suite, which systematically tests LDAP server implementations for various edge cases and malformed inputs, making it a well-documented and reproducible security issue.
The technical root cause of this vulnerability lies in improper memory management practices within the LDAP parsing routines of the Fedora Directory Server. When processing the malformed BER sequence, the server attempts to free memory that has not been properly initialized or allocated, resulting in memory corruption and subsequent system crash. This type of vulnerability falls under CWE-456, which specifically addresses "Use of Uninitialized Variable," and represents a classic example of improper memory handling that can lead to arbitrary code execution or system instability. The memory corruption occurs during the LDAP message processing phase where the server fails to validate the integrity of the incoming BER-encoded data before attempting memory operations on it. The uninitialized memory access creates a condition where the application attempts to release memory that contains unpredictable values, leading to the crash scenario described in the vulnerability report.
From an operational perspective, this vulnerability presents significant risks to organizations relying on Fedora Directory Server for directory services and authentication infrastructure. The remote exploit capability means that attackers can trigger the denial of service condition without requiring local access or authentication credentials, making it particularly dangerous in networked environments. The impact extends beyond simple service disruption as the crash can potentially affect the availability of directory services for legitimate users and applications that depend on the directory server for authentication, authorization, and directory lookups. This vulnerability can be exploited by attackers to create persistent service interruptions, potentially disrupting business operations and user access to systems that rely on directory services for authentication mechanisms.
Organizations should implement immediate mitigations including applying the vendor-provided security patches or updates that address the memory handling issues in the LDAP component. System administrators should also consider network segmentation and access controls to limit exposure of the directory server to untrusted networks. Monitoring for unusual LDAP traffic patterns and implementing intrusion detection systems can help identify exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management in server applications, aligning with ATT&CK technique T1499.004 for Network Denial of Service and emphasizing the need for robust error handling mechanisms in enterprise directory services. Organizations should also conduct thorough testing of their directory services after applying patches to ensure that the fix properly resolves the uninitialized memory access issue without introducing new stability concerns.