CVE-2011-3761 in NuSOAP
Summary
by MITRE
NuSOAP 0.9.5 allows remote attackers to obtain sensitive information via a direct request to a .php file, which reveals the installation path in an error message, as demonstrated by nuSOAP/classes/class.wsdl.php and certain other files.
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Analysis
by VulDB Data Team • 02/10/2019
The vulnerability identified as CVE-2011-3761 affects NuSOAP version 0.9.5, a popular PHP web services library that implements the SOAP protocol for creating and consuming web services. This issue represents a classic information disclosure vulnerability that occurs when applications fail to properly handle error conditions and expose sensitive system information to unauthorized users. The flaw specifically manifests in the error handling mechanisms of the NuSOAP library where direct requests to PHP files can trigger error messages containing the absolute installation path of the web application. This vulnerability falls under the CWE-200 category of "Information Exposure" and represents a significant security risk as it provides attackers with critical system information that can be leveraged for further exploitation attempts.
The technical implementation of this vulnerability involves the library's handling of malformed requests or direct access to internal PHP files without proper validation. When attackers make direct requests to files such as nuSOAP/classes/class.wsdl.php or other related components, the system generates error messages that inadvertently reveal the full filesystem path where the application is installed. This occurs because the error handling code does not sanitize or filter error messages before displaying them to users, allowing the complete installation path to be exposed. The vulnerability is particularly dangerous because it requires no authentication or special privileges to exploit, making it an easy target for automated scanning tools and malicious actors seeking to gather reconnaissance information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with crucial system information that can be used in subsequent attack phases. The exposed installation paths can reveal directory structures, file locations, and potentially even version information that could help attackers identify other vulnerabilities or tailor their attacks against specific system configurations. This information disclosure can serve as a stepping stone for more sophisticated attacks including path traversal, local file inclusion, or remote code execution attempts that might be possible if the attacker can leverage the exposed paths to manipulate the application's behavior. The vulnerability demonstrates poor security practices in error handling and input validation that are commonly found in legacy web applications.
Mitigation strategies for this vulnerability should focus on implementing proper error handling and input validation within the application. The most effective immediate solution involves modifying the error handling code to prevent sensitive information from being displayed in error messages to end users. This includes implementing custom error handlers that sanitize all error output and ensure that system paths are never exposed to remote users. Organizations should also implement proper access controls that prevent direct access to internal PHP files, using .htaccess rules or similar mechanisms to restrict access to application components. The remediation aligns with ATT&CK technique T1082 for system information discovery and emphasizes the importance of proper error handling as outlined in the OWASP Top Ten. Additionally, upgrading to a newer version of NuSOAP or migrating to more modern web services libraries that properly handle error conditions would provide a more comprehensive solution to this information disclosure vulnerability.