CVE-2023-27217: Belkin F7c063 Firmware DoS Vulnerability

CVE-2023-27217 Overview

CVE-2023-27217 is a stack-based buffer overflow vulnerability affecting the Belkin Smart Outlet V2 (F7C063) IoT device. The flaw exists in the ChangeFriendlyName() function of the device firmware, which fails to properly validate the length of user-supplied input. Attackers can exploit this vulnerability by sending a specially crafted UPnP (Universal Plug and Play) request to the device, potentially causing a Denial of Service (DoS) condition and compromising device availability on the network.

Critical Impact

This vulnerability allows unauthenticated remote attackers to crash affected Belkin Smart Outlet devices via crafted UPnP requests, disrupting smart home automation and potentially affecting connected electrical appliances.

Affected Products

• Belkin Smart Outlet V2 (F7C063)
• Belkin F7C063 Firmware version 2.00.11420.OWRT.PVT_SNSV2
• Belkin Wemo Mini Smart Plug V2 devices running vulnerable firmware

Discovery Timeline

• 2023-05-18 - CVE-2023-27217 published to NVD
• 2025-01-22 - Last updated in NVD database

Technical Details for CVE-2023-27217

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), specifically a stack-based buffer overflow condition. The vulnerable ChangeFriendlyName() function in the Belkin Smart Outlet firmware processes UPnP requests that allow users to modify the device's friendly name for identification purposes. However, the function does not implement adequate bounds checking on the input string length before copying it to a fixed-size stack buffer.

When an attacker sends a UPnP request containing an excessively long friendly name string, the function attempts to copy this data into the undersized buffer, overwriting adjacent memory on the stack. This memory corruption leads to unpredictable device behavior, typically resulting in a crash and denial of service condition. The network-accessible nature of UPnP services means this attack can be performed remotely without authentication.

Root Cause

The root cause of CVE-2023-27217 is improper input validation in the ChangeFriendlyName() function. The firmware code allocates a fixed-size buffer on the stack to store the device's friendly name but fails to validate that incoming UPnP request data fits within this buffer boundary. This classic buffer overflow pattern is particularly dangerous in embedded IoT devices where memory protection mechanisms like ASLR and stack canaries may be absent or weakly implemented.

Attack Vector

The attack is executed over the network via the UPnP protocol, which the Belkin Smart Outlet exposes for device discovery and configuration. An attacker on the same network segment (or with access via port forwarding/misconfiguration) can craft a malicious UPnP SOAP request targeting the ChangeFriendlyName action with an oversized payload. Since UPnP typically requires no authentication, any network-adjacent attacker can trigger this vulnerability. The attack does not require user interaction and can be automated to persistently disrupt device operation.

The vulnerability mechanism involves sending a specially crafted UPnP SOAP request to the device's service endpoint. The malicious request contains an excessively long string in the FriendlyName parameter, which exceeds the expected buffer size allocated in the ChangeFriendlyName() function. When the device processes this request, the oversized string overwrites the stack buffer boundaries, corrupting adjacent memory and causing the device to crash. For detailed technical analysis, see the Sternum IoT Blog Vulnerability Analysis.

Detection Methods for CVE-2023-27217

Indicators of Compromise

• Unexpected device reboots or offline status of Belkin Smart Outlet V2 devices
• Anomalous UPnP traffic patterns targeting port 49153 or similar UPnP service ports
• UPnP SOAP requests with unusually large FriendlyName parameter values (exceeding typical device name lengths)
• Network logs showing repeated connection attempts to IoT device UPnP endpoints

Detection Strategies

• Deploy network intrusion detection rules to identify malformed or oversized UPnP requests targeting IoT devices
• Monitor for UPnP traffic containing abnormally long string parameters in SOAP action requests
• Implement IoT network segmentation and log all cross-segment traffic attempts
• Use SentinelOne Singularity to detect anomalous network behavior patterns associated with IoT exploitation attempts

Monitoring Recommendations

• Enable UPnP traffic logging on network firewalls and analyze for suspicious payload sizes
• Configure alerts for repeated Belkin device offline events that may indicate active exploitation
• Perform regular firmware version audits of IoT devices to identify vulnerable firmware versions
• Deploy network-level anomaly detection to identify attack patterns against IoT infrastructure

How to Mitigate CVE-2023-27217

Immediate Actions Required

• Isolate affected Belkin Smart Outlet V2 devices on a separate network segment with restricted access
• Disable UPnP on network routers and firewalls to prevent external exploitation
• Check for and apply any available firmware updates from Belkin for the F7C063 device
• Consider replacing vulnerable devices if no firmware patch is available from the vendor

Patch Information

As of the last NVD update (2025-01-22), no specific vendor patch information is available in the CVE data. Users should monitor Belkin's official support channels for firmware updates addressing this vulnerability. In the absence of a vendor patch, network-level mitigations become critical for protecting affected devices.

Workarounds

• Disable UPnP functionality on the network router to prevent UPnP-based attacks
• Place IoT devices including the Belkin Smart Outlet on a dedicated VLAN with no direct internet access
• Implement firewall rules to block unsolicited inbound traffic to IoT device ports
• Consider using a dedicated IoT security gateway to filter and inspect traffic to smart home devices

Network isolation can be achieved by configuring your router's firewall to restrict UPnP traffic. On most enterprise firewalls, create rules to block incoming UPnP discovery (UDP port 1900) and UPnP service ports (typically TCP 49152-49154) from untrusted network segments. Additionally, segment IoT devices into a dedicated VLAN and apply strict access control policies to limit communication paths to only necessary management interfaces.