CVE-2001-1319 in Exchange
Summary
by MITRE
Microsoft Exchange 5.5 2000 allows remote attackers to cause a denial of service (hang) via exceptional BER encodings for the LDAP filter type field, as demonstrated by the PROTOS LDAPv3 test suite.
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Analysis
by VulDB Data Team • 12/23/2024
Microsoft Exchange 5.5 and 2000 servers contain a critical vulnerability in their Lightweight Directory Access Protocol implementation that can be exploited to cause a remote denial of service condition. This vulnerability specifically affects the LDAP filter type field processing within the Exchange server's directory service interface, where the system fails to properly handle exceptional Basic Encoding Rules (BER) encodings. The flaw manifests when malformed BER encoded data is sent to the LDAP service, causing the server to enter a hung state where it becomes unresponsive to legitimate requests. The vulnerability was demonstrated through the PROTOS LDAPv3 test suite, which contains specific test cases designed to identify weaknesses in LDAP implementation. This issue represents a classic buffer overflow or parsing vulnerability that falls under the CWE-121 category of buffer overflow conditions, though it manifests as a denial of service rather than arbitrary code execution. The attack vector requires a remote attacker to send specially crafted LDAP requests containing malformed BER encodings that exploit the server's insufficient input validation mechanisms. When the Exchange server attempts to process these invalid encodings, the parsing logic becomes trapped in an infinite loop or encounters a fatal error state that causes the service to hang indefinitely. The operational impact of this vulnerability is severe as it can completely disrupt directory services for an organization, preventing users from accessing email services, calendar functionality, and other directory-based applications that depend on the Exchange server's LDAP interface. This type of vulnerability aligns with ATT&CK technique T1499.004 which involves network denial of service attacks against services, and represents a significant weakness in the server's input sanitization and error handling capabilities. Organizations utilizing Microsoft Exchange 5.5 or 2000 should immediately implement mitigations including network segmentation to restrict LDAP access, implementing firewall rules to limit LDAP traffic, and applying available patches from Microsoft to address this specific BER encoding vulnerability. The vulnerability underscores the importance of proper input validation and robust error handling in directory services, as even seemingly benign malformed data can cause critical service disruptions in enterprise email systems.