CVE-2000-0783 in Firebox
Summary
by MITRE
Watchguard Firebox II allows remote attackers to cause a denial of service by sending a malformed URL to the authentication service on port 4100.
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Analysis
by VulDB Data Team • 05/27/2018
The CVE-2000-0783 vulnerability affects Watchguard Firebox II firewall appliances that implement an authentication service on port 4100. This particular flaw represents a classic denial of service attack vector that exploits improper input validation within the authentication subsystem. The vulnerability manifests when remote attackers craft and send malformed URLs to the authentication service, causing the system to crash or become unresponsive. This issue directly impacts the availability of the firewall's authentication capabilities, which are critical for network security operations and user access control.
The technical root cause of this vulnerability lies in the insufficient validation of URL parameters within the authentication service implementation. When the system receives malformed URL data, it fails to properly handle the malformed input, leading to a system crash or resource exhaustion that results in denial of service. This type of vulnerability falls under CWE-20, which describes improper input validation, and represents a common class of flaws that occur when applications fail to properly sanitize or validate user-supplied data before processing. The vulnerability specifically affects the authentication service running on TCP port 4100, which is a well-known port used by Watchguard firewalls for their authentication protocols.
From an operational impact perspective, this vulnerability creates significant security and availability concerns for organizations relying on Watchguard Firebox II appliances. The denial of service condition effectively prevents legitimate users from accessing network resources through the authentication system, potentially disrupting business operations and creating security gaps where unauthorized access could occur. The attack requires minimal technical expertise to execute, making it particularly dangerous as it can be exploited by both skilled attackers and less sophisticated threat actors. Network administrators face the challenge of maintaining service availability while dealing with the potential for repeated attacks that could cause persistent disruption to network access controls.
Organizations should implement immediate mitigations including network segmentation to restrict access to port 4100, firewall rules to limit connections to the authentication service, and monitoring systems to detect anomalous URL patterns. The vulnerability highlights the importance of input validation and proper error handling in network services, aligning with ATT&CK technique T1499.004 for network denial of service attacks. System administrators should also consider implementing intrusion detection systems that can identify malformed URL patterns targeting authentication services and apply vendor-supplied patches or firmware updates as soon as they become available. The incident underscores the critical need for robust input validation practices in network security appliances and demonstrates how seemingly simple input handling flaws can result in significant availability impacts.