CVE-2007-0138 in Formbankserver
Summary
by MITRE
formbankcgi.exe in Fersch Formbankserver 1.9, when the PATH_INFO begins with (1) AbfrageForm or (2) EingabeForm, allows remote attackers to cause a denial of service (daemon crash) via multiple requests containing many /../ sequences in the Name parameter. NOTE: The provenance of this information is unknown; the details are obtained solely from third party information.
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Analysis
by VulDB Data Team • 08/13/2018
The vulnerability identified as CVE-2007-0138 affects the Fersch Formbankserver 1.9 web application server, specifically targeting the formbankcgi.exe component. This issue represents a classic path traversal attack vector that exploits improper input validation mechanisms within the application's handling of URL paths. The vulnerability manifests when the PATH_INFO parameter begins with either "AbfrageForm" or "EingabeForm" strings, creating a condition where malicious actors can manipulate the Name parameter to include excessive "../" sequences that ultimately trigger system instability. The attack requires no authentication and can be executed remotely, making it particularly dangerous for web applications that process user input through CGI interfaces.
The technical flaw resides in the insufficient sanitization and validation of user-supplied input within the formbankcgi.exe executable. When processing requests containing the specified PATH_INFO prefixes, the application fails to properly validate or limit the depth of directory traversal sequences in the Name parameter. This weakness creates a path traversal condition where multiple "../" sequences can cause the application to attempt to access directories outside the intended application scope, leading to resource exhaustion or memory corruption. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The implementation of such attacks typically involves crafting malicious URLs that exploit insufficient input validation to navigate through the file system hierarchy.
The operational impact of this vulnerability extends beyond simple denial of service conditions, potentially leading to complete daemon crashes that can disrupt business operations for the affected organization. Remote attackers can repeatedly submit malicious requests containing excessive directory traversal sequences, causing the formbankcgi.exe process to consume excessive system resources or encounter fatal errors that result in application termination. This type of attack can be particularly effective when combined with automated scanning tools or distributed denial of service techniques, amplifying the disruption potential. The vulnerability demonstrates a fundamental lack of input validation and resource management within the web application server, creating opportunities for attackers to destabilize critical business processes that rely on form processing functionality.
Mitigation strategies for this vulnerability should focus on implementing robust input validation mechanisms that prevent excessive directory traversal sequences from being processed by the application. Organizations should deploy web application firewalls or security filters that can detect and block requests containing multiple "../" sequences in parameters that are processed by CGI executables. The implementation of proper access controls and directory restriction mechanisms within the web server configuration can help prevent unauthorized access to system resources. Additionally, regular patching and updating of web applications, along with comprehensive input sanitization routines that limit parameter length and validate character sequences, can effectively address this class of vulnerability. Security monitoring should include detection of unusual request patterns containing excessive path traversal sequences, as outlined in the ATT&CK framework under technique T1210 for exploiting weaknesses in remote services. The vulnerability highlights the importance of implementing defense-in-depth strategies that include both perimeter security controls and application-level input validation to prevent similar issues from compromising system availability and integrity.