CVE-2006-0452 in Fedora Core
Summary
by MITRE
dn2ancestor in the LDAP component in Fedora Directory Server 1.0 allows remote attackers to cause a denial of service (CPU and memory consumption) via a ModDN operation with a DN that contains a large number of "," (comma) characters, which results in a large amount of recursion, as demonstrated using the ProtoVer LDAP test suite.
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Analysis
by VulDB Data Team • 08/05/2017
The vulnerability identified as CVE-2006-0452 represents a critical denial of service flaw within the LDAP component of Fedora Directory Server version 1.0. This issue specifically affects the dn2ancestor functionality which processes distinguished names during directory operations. The vulnerability manifests when a ModDN operation is performed with a malformed distinguished name containing an excessive number of comma characters, creating a recursive processing condition that consumes disproportionate system resources.
The technical implementation of this vulnerability stems from insufficient input validation and recursive processing logic within the LDAP server's dn2ancestor function. When processing a distinguished name with numerous comma characters, the server enters into deep recursive operations that exponentially increase CPU utilization and memory consumption. The ProtoVer LDAP test suite demonstrates this vulnerability by crafting specific DN strings that trigger the recursive behavior, causing the server to consume all available system resources and ultimately resulting in a denial of service condition. This flaw operates at the application layer and can be exploited remotely without authentication requirements.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and stability. Attackers can consume all available CPU cycles and memory resources, effectively rendering the LDAP server unresponsive to legitimate requests. This type of denial of service attack can have cascading effects throughout directory services that depend on the affected server, potentially impacting authentication, authorization, and directory lookup services across the entire infrastructure. The vulnerability is particularly dangerous in environments where LDAP servers serve as critical backend services for enterprise applications and user authentication systems.
Mitigation strategies for this vulnerability require immediate implementation of input validation controls and resource limiting measures. System administrators should implement rate limiting and maximum recursion depth controls within the LDAP server configuration to prevent excessive processing of malformed distinguished names. The recommended approach includes configuring maximum allowed DN length parameters and implementing recursive call depth limits to prevent the exploitation of the vulnerable dn2ancestor function. Additionally, deploying network-level firewalls and intrusion prevention systems can help detect and block malicious LDAP operations before they reach the vulnerable server components. Organizations should also consider upgrading to patched versions of Fedora Directory Server or implementing compensating controls such as LDAP proxy servers that can validate and sanitize incoming requests before forwarding them to the vulnerable backend systems. This vulnerability aligns with CWE-674 principle of uncontrolled recursion and represents a classic example of insufficient input validation that can be addressed through proper defensive programming practices and resource management controls.