CVE-2016-6255 in libupnp
Summary
by MITRE
Portable UPnP SDK (aka libupnp) before 1.6.21 allows remote attackers to write to arbitrary files in the webroot via a POST request without a registered handler.
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Analysis
by VulDB Data Team • 07/10/2024
The Portable UPnP SDK known as libupnp versions prior to 1.6.21 contain a critical vulnerability that enables remote attackers to perform arbitrary file writes within the webroot directory through crafted POST requests. This vulnerability stems from insufficient input validation and improper handling of HTTP requests that lack registered handlers, creating a path for malicious actors to exploit the system's file writing capabilities. The flaw exists at the protocol implementation level where the SDK fails to properly authenticate or validate the legitimacy of file write operations initiated through HTTP POST methods, particularly when no specific handler has been registered for the requested resource.
The technical nature of this vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The vulnerability operates by leveraging the UPnP protocol's HTTP server implementation to process incoming requests without adequate validation of the target file paths. When an attacker sends a POST request to the UPnP device, the system processes the request through a default handler that does not properly verify whether the requested file operation is authorized or legitimate. This creates a condition where the device will write content to any file path specified in the request, as long as it resides within the webroot directory, allowing for arbitrary file creation or modification.
From an operational perspective, this vulnerability poses significant risks to networked devices that utilize libupnp for UPnP functionality, including routers, network attached storage devices, smart home appliances, and other internet of things devices. Attackers can leverage this vulnerability to upload malicious files, overwrite critical system components, or establish persistence mechanisms within the device's file system. The impact extends beyond simple file manipulation as it can potentially allow for privilege escalation, denial of service conditions, or even complete device compromise. The remote nature of the attack means that adversaries do not require physical access to the device or network credentials to exploit this vulnerability, making it particularly dangerous in enterprise and consumer environments where such devices are commonly deployed without proper security hardening.
The attack vector specifically targets devices that rely on libupnp for UPnP service implementations, which are prevalent in home and enterprise networks. This vulnerability demonstrates a fundamental flaw in the SDK's security model where the assumption is made that all HTTP requests within the webroot context are legitimate, without proper authentication or authorization checks. The lack of proper handler registration validation creates an implicit trust model that can be easily subverted by remote attackers. Organizations and device manufacturers should consider implementing additional security measures such as input sanitization, path validation, and proper access control mechanisms to prevent unauthorized file operations.
Mitigation strategies for this vulnerability include immediate upgrading to libupnp version 1.6.21 or later, which contains the necessary patches to address the improper file handling behavior. Network administrators should also implement proper firewall rules to restrict access to UPnP ports and services where possible, particularly in environments where UPnP is not required. Additionally, device manufacturers should consider implementing more robust input validation and authentication mechanisms within their UPnP implementations, ensuring that all file operations are properly validated against a whitelist of allowed paths and operations. The vulnerability serves as a reminder of the importance of secure coding practices in network protocols and the need for comprehensive security testing of protocol implementations to prevent similar issues from occurring in other software components.
This vulnerability relates to several ATT&CK techniques including T1059.007 for command and scripting interpreter and T1078.004 for valid accounts, as exploitation may lead to persistent access through file manipulation. Organizations should also consider implementing network monitoring solutions to detect anomalous file write operations that could indicate exploitation attempts, particularly in environments where UPnP services are enabled but not properly secured. The vulnerability highlights the critical need for proper security controls in embedded systems and IoT devices where protocol implementations may not receive the same level of security scrutiny as enterprise applications.