CVE-2017-6367 in FTP Server
Summary
by MITRE
In Cerberus FTP Server 8.0.10.1, a crafted HTTP request causes the Windows service to crash. The attack methodology involves a long Host header and an invalid Content-Length header.
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Analysis
by VulDB Data Team • 12/03/2025
The vulnerability identified as CVE-2017-6367 represents a critical denial of service flaw within Cerberus FTP Server version 8.0.10.1 that specifically targets the Windows service component through carefully crafted HTTP requests. This vulnerability exploits a fundamental weakness in the server's request handling mechanism, where the service fails to properly validate and process malformed HTTP headers. The attack vector leverages two specific header manipulations: a lengthy Host header and an invalid Content-Length header, both of which trigger unexpected behavior in the server's processing pipeline. The combination of these malformed headers creates a condition that causes the Windows service to terminate abruptly, resulting in a complete service disruption that affects all connected clients and legitimate users. This vulnerability directly impacts the availability aspect of the CIA triad, rendering the FTP server inoperable until manual intervention or service restart occurs.
The technical exploitation of this vulnerability stems from inadequate input validation within the HTTP request processing module of the Cerberus FTP Server. When the Windows service receives a request containing an excessively long Host header combined with an invalid Content-Length value, the server's parsing logic encounters a buffer overflow condition or memory corruption scenario. This condition typically occurs because the server attempts to allocate memory based on the invalid Content-Length value while simultaneously processing the extended Host header data. The flaw falls under CWE-122, which describes heap-based buffer overflow conditions, and more specifically aligns with CWE-129, representing improper validation of array indices. The vulnerability demonstrates characteristics of a stack-based buffer overflow when the service attempts to process the oversized header data without proper bounds checking mechanisms. The service's failure to implement robust input sanitization and validation creates an exploitable condition where malicious actors can trigger system instability through carefully constructed HTTP requests.
The operational impact of CVE-2017-6367 extends beyond simple service disruption to encompass broader security implications for organizations relying on Cerberus FTP Server for file transfer operations. When the Windows service crashes, all active FTP connections are terminated abruptly, potentially leading to data loss or corruption during incomplete transfers. Network administrators face significant challenges in maintaining service availability, as the vulnerability can be exploited remotely without requiring authentication credentials, making it particularly dangerous in production environments. The attack requires minimal sophistication and can be executed automatically through automated scanning tools, enabling widespread exploitation across multiple systems. Organizations may experience downtime that affects business operations, especially in scenarios where the FTP server serves as a critical component in data exchange processes. Additionally, the vulnerability could be leveraged as part of a larger attack chain, potentially serving as an initial compromise vector or as a method to create a distraction while other attack vectors are deployed, aligning with techniques documented in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks.
Mitigation strategies for CVE-2017-6367 require immediate implementation of both temporary workarounds and permanent architectural fixes. Organizations should apply the vendor-supplied patch or upgrade to a version of Cerberus FTP Server that addresses this vulnerability, as the manufacturer has released updates specifically targeting these buffer overflow conditions. Until patches are applied, network administrators can implement firewall rules to limit HTTP traffic to the FTP server, particularly blocking requests with unusually long Host headers or malformed Content-Length values. Input validation should be enhanced at the network perimeter through the deployment of web application firewalls that can detect and block such malformed requests before they reach the vulnerable service. System monitoring should be enhanced to detect unusual service termination patterns that may indicate exploitation attempts. Additionally, implementing rate limiting mechanisms can help prevent automated exploitation attempts by limiting the number of requests that can be processed within a given time period. Security teams should also conduct regular vulnerability assessments to identify similar input validation weaknesses in other network services and ensure that proper defensive measures such as address space layout randomization and stack canaries are implemented to provide additional layers of protection against similar buffer overflow exploits.