CVE-2001-0616 in Freestyle Chat
Summary
by MITRE
Faust Informatics Freestyle Chat server prior to 4.1 SR3 allows a remote attacker to create a denial of service via a URL request which includes a MS-DOS device name (e.g., GET /aux HTTP/1.0).
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Analysis
by VulDB Data Team • 10/05/2025
The vulnerability identified as CVE-2001-0616 affects the Faust Informatics Freestyle Chat server version 4.1 SR2 and earlier, representing a significant security flaw that enables remote attackers to execute denial of service attacks. This issue stems from the server's inadequate handling of specific URL requests containing Microsoft DOS device names, which are typically reserved system identifiers used in legacy operating systems. The vulnerability exploits the server's failure to properly sanitize incoming requests, allowing malicious actors to craft specially formatted HTTP GET requests that target these reserved device names.
The technical implementation of this vulnerability involves the server's processing of URLs that include MS-DOS device names such as aux, con, nul, prn, lpt1, com1, and similar identifiers. When the Freestyle Chat server receives a request like GET /aux HTTP/1.0, it attempts to process the request through its file system handling mechanisms without proper validation. This flaw falls under CWE-20, "Improper Input Validation," where the system fails to validate or sanitize input data before processing it, and can also be categorized under CWE-400, "Uncontrolled Resource Consumption," as the malformed requests can cause the server to consume excessive system resources or enter error states. The attack leverages the fact that these device names are treated specially by underlying operating systems, causing the server to potentially hang, crash, or become unresponsive when attempting to process such requests.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render the entire chat server unavailable to legitimate users. Remote attackers can exploit this weakness without requiring authentication or specialized knowledge, making it particularly dangerous in production environments where continuous availability is critical. The vulnerability demonstrates a fundamental flaw in the server's request parsing and validation logic, where the system fails to recognize that certain URL components are not legitimate resource requests but rather system artifacts that should be rejected or properly handled. This type of attack can be executed repeatedly, potentially causing sustained denial of service conditions that can last until the server is manually restarted or the vulnerability is patched.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization mechanisms within the Freestyle Chat server software. System administrators should immediately upgrade to version 4.1 SR3 or later, which contains the necessary patches to address this issue. Additionally, network-level protections such as firewall rules or web application firewalls can be configured to block requests containing known MS-DOS device names in URL paths. The implementation of these protections aligns with ATT&CK technique T1499.004, "Endpoint Denial of Service," and represents a fundamental security control that addresses the root cause of the vulnerability. Organizations should also consider implementing request rate limiting and monitoring mechanisms to detect and respond to abnormal request patterns that may indicate exploitation attempts. The vulnerability highlights the importance of input validation in web applications and demonstrates how legacy system artifacts can create security weaknesses when improperly handled in modern network services.