CVE-2017-3882 in CVR100W
Summary
by MITRE
A vulnerability in the Universal Plug-and-Play (UPnP) implementation in the Cisco CVR100W Wireless-N VPN Router could allow an unauthenticated, Layer 2-adjacent attacker to execute arbitrary code or cause a denial of service (DoS) condition. The remote code execution could occur with root privileges. The vulnerability is due to incomplete range checks of the UPnP input data, which could result in a buffer overflow. An attacker could exploit this vulnerability by sending a malicious request to the UPnP listening port of the targeted device. An exploit could allow the attacker to cause the device to reload or potentially execute arbitrary code with root privileges. This vulnerability affects all firmware releases of the Cisco CVR100W Wireless-N VPN Router prior to Firmware Release 1.0.1.22. Cisco Bug IDs: CSCuz72642.
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Analysis
by VulDB Data Team • 12/24/2020
The vulnerability identified as CVE-2017-3882 represents a critical security flaw within the Universal Plug-and-Play implementation of the Cisco CVR100W Wireless-N VPN Router. This device operates at the network infrastructure level, serving as a gateway for wireless connectivity and vpn services, making it a prime target for attackers seeking to compromise network perimeters. The vulnerability specifically resides in the UPnP service handling mechanism, which is designed to facilitate automatic network configuration and device discovery but has been improperly implemented to handle input validation. The flaw manifests as incomplete range checks on UPnP input data, creating conditions where maliciously crafted packets can trigger buffer overflow conditions within the router's processing routines. This type of vulnerability falls under the CWE-121 category of buffer overflow conditions, specifically manifesting as stack-based buffer overflow due to inadequate input validation. The attack vector requires an unauthenticated adversary to be positioned at Layer 2 adjacency, meaning they must be on the same network segment as the target device, which significantly reduces the attack surface but does not eliminate the risk. The operational impact of this vulnerability is severe, as it provides attackers with the capability to execute arbitrary code with root privileges, effectively granting them complete administrative control over the affected device. This level of privilege escalation allows for comprehensive system compromise, including the ability to modify network configurations, establish persistent backdoors, or extract sensitive information from the device. The potential for denial of service conditions further amplifies the threat, as attackers could render the device inoperable and disrupt network services. The vulnerability affects all firmware versions of the Cisco CVR100W prior to release 1.0.1.22, indicating that the flaw existed for an extended period without proper remediation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and command execution, specifically leveraging the T1059.007 sub-technique for command and scripting interpreter execution. The exploitation process requires sending malicious requests to the UPnP listening port, which typically operates on port 1900, making it a predictable target for automated scanning tools. The buffer overflow condition occurs when the router's UPnP implementation fails to properly validate the length of incoming data, allowing attackers to overflow the allocated buffer space and potentially overwrite critical program execution data. This vulnerability demonstrates a classic example of how network infrastructure devices often lack proper input sanitization mechanisms, particularly in services designed for ease of use and automatic configuration. The implications extend beyond simple device compromise, as the CVR100W serves as a network gateway, potentially providing attackers with access to internal network resources. Mitigation efforts should focus on immediate firmware updates to version 1.0.1.22 or later, which contain the necessary patches to address the incomplete range checks. Network segmentation and access control measures can help reduce the attack surface by limiting Layer 2 adjacency opportunities. Additionally, implementing network monitoring to detect unusual UPnP traffic patterns and disabling UPnP services when not required provides additional defensive layers. The vulnerability highlights the importance of proper input validation and bounds checking in network services, particularly those exposed to untrusted network traffic. Organizations should conduct thorough vulnerability assessments of their network infrastructure to identify similar implementations that may be susceptible to analogous buffer overflow conditions. The root cause of this vulnerability underscores the need for comprehensive security testing of network services, including both functional and security-oriented validation of input handling mechanisms. The impact of such vulnerabilities extends beyond immediate device compromise to potentially enable broader network infiltration and persistent access to enterprise environments.