CVE-2007-0087 in IIS
Summary
by MITRE
** DISPUTED ** Microsoft Internet Information Services (IIS), when accessed through a TCP connection with a large window size, allows remote attackers to cause a denial of service (network bandwidth consumption) via a Range header that specifies multiple copies of the same fragment. NOTE: the severity of this issue has been disputed by third parties, who state that the large window size required by the attack is not normally supported or configured by the server, or that a DDoS-style attack would accomplish the same goal.
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Analysis
by VulDB Data Team • 08/07/2024
This vulnerability affects Microsoft Internet Information Services when processing TCP connections with large window sizes, creating a potential denial of service condition through specific Range header manipulation. The flaw occurs when a remote attacker sends a Range header that contains multiple instances of identical data fragments, exploiting the way IIS handles these requests. The attack leverages the TCP window scaling mechanism to amplify network bandwidth consumption, effectively creating a resource exhaustion scenario that can disrupt legitimate service availability. The vulnerability is particularly concerning because it operates at the network protocol level rather than application level, making it difficult to distinguish from legitimate traffic patterns.
The technical implementation of this vulnerability involves the manipulation of HTTP Range requests combined with TCP window scaling features. When IIS processes a Range header containing repeated fragments, it attempts to fulfill each request component, leading to excessive network resource utilization. The attack requires a specific configuration where large TCP window sizes are enabled, which is not standard in typical server deployments. This mechanism allows attackers to consume network bandwidth proportional to the number of repeated fragments specified in the Range header, creating a sustained resource drain that can overwhelm network connections and reduce overall system responsiveness.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect network infrastructure capacity and overall system availability. Attackers can consume significant bandwidth resources through relatively simple HTTP requests, making this a cost-effective method for causing service degradation. The vulnerability's effectiveness depends on the server's TCP window scaling configuration, which may not be enabled in default deployments, but when present, creates a substantial risk for systems that handle HTTP content delivery. Organizations may experience cascading effects where network bandwidth exhaustion impacts other services and applications running on the same infrastructure.
Security professionals should consider this vulnerability in the context of broader denial of service attack patterns and network protocol analysis. The issue aligns with CWE-400, which addresses unchecked resource consumption in network applications, and can be categorized under ATT&CK technique T1498 for network denial of service attacks. Mitigation strategies should focus on implementing proper TCP window scaling controls, configuring rate limiting for HTTP requests, and monitoring for unusual Range header patterns. Network administrators should also consider implementing intrusion detection systems that can identify and block malformed Range headers that contain excessive repeated fragments, while ensuring that server configurations do not unnecessarily enable large TCP window sizes that could amplify the attack vector.