CVE-2005-0451 in HTTP Server
Summary
by MITRE
Sami HTTP Server 1.0.5 allows remote attackers to cause a denial of service via an HTTP request containing two CRLF sequences, which triggers a NULL dereference.
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Analysis
by VulDB Data Team • 07/01/2021
The vulnerability identified as CVE-2005-0451 affects the Sami HTTP Server version 1.0.5, representing a critical denial of service flaw that can be exploited by remote attackers through carefully crafted HTTP requests. This vulnerability demonstrates a fundamental issue in input validation and memory management within the server's request processing pipeline, where the system fails to properly handle malformed HTTP protocol sequences.
The technical flaw manifests when an attacker submits an HTTP request containing two consecutive CRLF (Carriage Return Line Feed) sequences, which are standard protocol terminators used in HTTP communications. The server's parsing logic does not adequately validate these sequences, causing the application to attempt to dereference a NULL pointer during request processing. This NULL dereference results in an immediate application crash or termination, effectively rendering the web server unavailable to legitimate users and causing a denial of service condition that impacts system availability and service continuity.
This vulnerability directly maps to CWE-476, which describes NULL pointer dereference conditions in software implementations, and represents a classic example of improper input validation leading to application instability. The attack vector is particularly concerning as it requires minimal complexity to execute, making it an attractive target for malicious actors seeking to disrupt services. The vulnerability operates at the protocol level, affecting the HTTP server's ability to process valid requests and maintain operational continuity.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged in coordinated attacks against web applications and infrastructure. Attackers can systematically exploit this weakness to repeatedly crash the server, potentially leading to extended downtime and service degradation that affects business operations and user access. The vulnerability also highlights the importance of robust error handling and memory management practices in server applications, particularly those handling network protocols where malformed input is common.
Mitigation strategies should include immediate patching of the Sami HTTP Server to version 1.0.6 or later, which contains the necessary fixes for proper CRLF sequence handling. Network administrators should implement input validation at the perimeter using firewalls and intrusion prevention systems to filter out malformed HTTP requests containing excessive CRLF sequences. Additionally, deploying application-level protections such as request rate limiting and protocol validation can help reduce the effectiveness of exploitation attempts. The vulnerability also underscores the necessity of comprehensive security testing including protocol compliance verification and memory safety analysis as part of the software development lifecycle, aligning with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also consider implementing redundant systems and failover mechanisms to maintain service availability during potential exploitation attempts, as this vulnerability represents a fundamental architectural weakness that could be exploited in larger attack campaigns targeting web infrastructure.