CVE-2004-1973 in Web Server
Summary
by MITRE
DiGi Web Server allows remote attackers to cause a denial of service (CPU consumption) via an HTTP GET request that contains a large number of / (slash) characters, which consumes resources when DiGi converts the slashes to \ (backslash) characters.
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Analysis
by VulDB Data Team • 01/06/2025
The vulnerability identified as CVE-2004-1973 affects the DiGi Web Server implementation and represents a classic example of a resource exhaustion attack that targets the server's handling of malformed HTTP requests. This issue demonstrates how seemingly benign operations can be exploited to create significant operational disruptions in web server environments.
The technical flaw resides in the server's URL parsing mechanism where it processes incoming HTTP GET requests containing an excessive number of forward slash characters. When these requests are received, the DiGi Web Server attempts to normalize the URL path by converting each forward slash character into a backslash character for internal processing. This conversion process becomes computationally expensive when dealing with requests containing thousands or millions of consecutive slashes, as the server must iterate through and transform each character individually.
The operational impact of this vulnerability manifests as sustained high CPU utilization on the affected server, effectively causing a denial of service condition for legitimate users. Attackers can exploit this weakness by sending specially crafted HTTP GET requests with an excessive number of slashes, which causes the server to consume disproportionate amounts of processing power during the URL normalization phase. The server becomes unresponsive to other legitimate requests while it processes the malformed input, resulting in service disruption for all users attempting to access the web server.
This vulnerability aligns with CWE-400, which categorizes resource exhaustion issues in software systems, and demonstrates how improper input validation can lead to system instability. From an ATT&CK framework perspective, this represents a denial of service attack using resource exhaustion techniques that fall under the T1499.004 sub-technique for network denial of service attacks. The vulnerability also illustrates the importance of proper input sanitization and bounds checking in web server implementations.
Mitigation strategies should focus on implementing rate limiting mechanisms to prevent excessive requests from a single source, establishing reasonable limits on URL path complexity, and configuring the server to reject requests containing an excessive number of consecutive special characters. Additionally, updating to patched versions of the DiGi Web Server software would address the root cause of this vulnerability, while implementing proper input validation and normalization routines would prevent similar issues from occurring in other components of the web infrastructure. Organizations should also consider deploying web application firewalls to detect and block such malicious traffic patterns before they reach the vulnerable server components.