CVE-2006-4518 in WinGate
Summary
by MITRE
Qbik WinGate 6.1.4 and earlier allows remote attackers to cause a denial of service (CPU consumption) via a DNS request with a self-referencing compressed name pointer, which triggers an infinite loop.
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Analysis
by VulDB Data Team • 06/16/2025
The vulnerability identified as CVE-2006-4518 affects Qbik WinGate 6.1.4 and earlier versions, representing a critical denial of service weakness in the DNS resolution process. This flaw resides within the handling of DNS requests containing self-referencing compressed name pointers, which creates a condition where the system enters an infinite loop during processing. The vulnerability specifically targets the DNS server functionality within the WinGate software, which serves as a gateway for network traffic and provides various filtering and caching services. When a maliciously crafted DNS request is received, the system's DNS resolver fails to properly validate the compressed name pointer structure, leading to recursive processing that never terminates.
The technical exploitation of this vulnerability occurs through the manipulation of DNS message format, specifically targeting the compression mechanism used in DNS names. In standard DNS implementations, name compression allows for efficient transmission by replacing repeated domain names with pointers to their first occurrence. However, when a pointer references itself within the same DNS message, the resolver enters an infinite loop as it attempts to resolve the pointer to its own location. This self-referencing condition creates a recursive processing scenario where the system continuously follows the pointer back to itself, consuming CPU resources indefinitely. The flaw exists at the protocol parsing level where input validation is insufficient to detect and reject malformed compressed name pointers that create circular references.
From an operational perspective, this vulnerability poses significant risks to network availability and system stability. The denial of service condition caused by excessive CPU consumption can render the affected WinGate appliance unusable for legitimate network traffic, effectively disrupting services for all connected users. The infinite loop consumes system resources without bounds, potentially leading to complete system exhaustion and requiring manual intervention to restore normal operation. Network administrators may experience service interruptions that impact business operations, particularly in environments where WinGate serves as a critical gateway for internet access or internal network filtering. The vulnerability is particularly concerning because it can be exploited remotely without requiring authentication, making it accessible to any attacker who can send DNS requests to the vulnerable system.
The impact of this vulnerability aligns with CWE-121, which addresses buffer overflow conditions that can lead to denial of service through resource exhaustion. The flaw demonstrates characteristics consistent with the ATT&CK technique T1499.004, which involves network denial of service attacks that consume system resources. Organizations using Qbik WinGate 6.1.4 or earlier versions should prioritize immediate remediation through software updates to address the DNS parsing vulnerability. The recommended mitigation strategy involves upgrading to a patched version of WinGate that implements proper input validation for DNS compressed name pointers. Additionally, network administrators should consider implementing DNS filtering rules that can detect and block malformed DNS requests, though this represents a temporary workaround rather than a permanent solution. The vulnerability underscores the importance of robust input validation in network protocol implementations and highlights the need for comprehensive testing of edge cases in DNS handling code. Organizations should also implement monitoring systems to detect unusual CPU consumption patterns that may indicate exploitation attempts, while ensuring that security patches are applied promptly to prevent potential exploitation by threat actors seeking to disrupt network services.