CVE-2002-0511 in nscd
Summary
by MITRE
The default configuration of Name Service Cache Daemon (nscd) in Caldera OpenLinux 3.1 and 3.1.1 uses cached PTR records instead of consulting the authoritative DNS server for the A record, which could make it easier for remote attackers to bypass applications that restrict access based on host names.
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Analysis
by VulDB Data Team • 06/20/2024
The vulnerability described in CVE-2002-0511 represents a critical flaw in the Name Service Cache Daemon (nscd) implementation within Caldera OpenLinux versions 3.1 and 3.1.1. This issue stems from the default configuration where nscd prioritizes cached PTR records over direct consultation of authoritative DNS servers when resolving A records. The fundamental problem lies in the cache daemon's behavior of using stale or cached reverse DNS information rather than performing real-time authoritative lookups, creating a security gap that can be exploited by malicious actors.
The technical flaw manifests when applications implement host-based access controls that rely on hostname resolution for security decisions. When nscd returns cached PTR records instead of querying authoritative servers, it can provide incorrect or outdated hostname mappings that bypass security mechanisms designed to restrict access based on hostnames. This behavior creates a situation where an attacker could potentially exploit the caching mechanism to gain unauthorized access to systems that should be restricted based on hostname validation. The vulnerability specifically targets the nscd service which is responsible for caching name service lookups to improve performance, but the default configuration fails to properly balance performance optimization with security requirements.
From an operational impact perspective, this vulnerability enables remote attackers to circumvent hostname-based access controls that are commonly implemented in network security architectures. Applications that depend on host name validation for access restriction can be bypassed, potentially allowing unauthorized users to gain access to restricted resources. The attack vector is particularly concerning because it operates at the name resolution level, affecting the fundamental security mechanisms that rely on hostname verification. This vulnerability can be exploited by attackers who understand the caching behavior and can manipulate or predict the cached results to gain unauthorized access to systems that should be protected by hostname-based restrictions.
The security implications of this vulnerability align with CWE-200, which addresses information exposure through improper information gathering, and can be mapped to ATT&CK technique T1071.004 for application layer protocol usage. The flaw demonstrates a classic case of insufficient input validation and improper information handling in network services. Organizations should implement immediate mitigations including disabling the problematic caching behavior, configuring nscd to properly query authoritative servers, or implementing additional access control measures that do not rely solely on hostname validation. Regular monitoring of nscd cache behavior and implementing proper security testing procedures can help identify and prevent exploitation of this vulnerability in production environments.