CVE-2009-4587 in Cherokee
Summary
by MITRE
Cherokee Web Server 0.5.4 allows remote attackers to cause a denial of service (daemon crash) via an MS-DOS reserved word in a URI, as demonstrated by the AUX reserved word.
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Analysis
by VulDB Data Team • 09/23/2025
The Cherokee Web Server version 0.5.4 contains a critical vulnerability that enables remote attackers to induce a denial of service condition through carefully crafted URI requests. This vulnerability specifically targets the server's handling of Microsoft DOS reserved words within Uniform Resource Identifiers, creating a scenario where legitimate web traffic can be exploited to crash the daemon process. The attack vector demonstrates how legacy operating system conventions can create unexpected security implications in modern web server implementations, particularly when input validation mechanisms fail to account for historical naming conventions that should be restricted.
The technical flaw stems from inadequate input sanitization within the web server's URI parsing component. When the Cherokee server encounters a URI containing MS-DOS reserved words such as AUX, CON, PRN, COM1, LPT1, and similar constructs, the server's internal processing logic fails to properly handle these reserved identifiers. This processing failure results in an unhandled exception or memory corruption that ultimately causes the web server daemon to terminate abruptly. The vulnerability operates at the application layer and requires no authentication or privileged access, making it particularly dangerous as it can be exploited by any remote attacker with knowledge of the target server's address. This type of flaw aligns with CWE-20, representing improper input validation where the system fails to properly sanitize user-supplied data before processing.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent availability issues for web applications. When exploited successfully, the daemon crash forces administrators to manually restart the web server service, potentially causing extended downtime for legitimate users. In high-availability environments, this vulnerability could be particularly damaging as it may be used as part of a broader attack strategy to degrade service quality or mask other malicious activities. The vulnerability also demonstrates how legacy system conventions can create security gaps in modern software implementations, particularly in environments where web servers must maintain compatibility with various client request formats while simultaneously defending against malicious input.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and sanitization mechanisms within the web server configuration. Administrators should consider implementing URI filtering rules that reject or normalize requests containing MS-DOS reserved words before they reach the core processing logic. The recommended approach involves configuring the web server to either strip or encode these reserved identifiers from incoming URIs, preventing the daemon from encountering malformed input that could trigger the crash condition. Additionally, system administrators should implement monitoring solutions to detect unusual patterns of daemon restarts that may indicate exploitation attempts. This vulnerability highlights the importance of following secure coding practices and adhering to industry standards such as those outlined in the OWASP Top Ten project, which emphasizes the need for proper input validation and error handling to prevent application-level crashes and service disruptions.
The attack scenario demonstrates characteristics consistent with the ATT&CK framework's privilege escalation and denial of service tactics, where adversaries leverage application-level weaknesses to compromise system availability. This particular vulnerability represents a low-complexity attack that can be automated and executed at scale, making it attractive to threat actors seeking to disrupt web services without requiring significant technical expertise. The exploitation of this vulnerability also underscores the importance of regular security updates and patch management programs, as this issue would likely be resolved through version upgrades that implement proper input validation mechanisms. Organizations should consider implementing network-level protections such as web application firewalls that can detect and block requests containing known problematic patterns, providing an additional layer of defense against this specific class of attack.