CVE-2025-5622: D-Link DIR-816 Buffer Overflow Vulnerability

CVE-2025-5622 Overview

A critical stack-based buffer overflow vulnerability has been discovered in D-Link DIR-816 firmware version 1.10CNB05. The vulnerability exists in the wirelessApcli_5g function within the /goform/wirelessApcli_5g file. Improper handling of the apcli_mode_5g, apcli_enc_5g, and apcli_default_key_5g arguments allows attackers to trigger a stack-based buffer overflow condition. This vulnerability can be exploited remotely without authentication, potentially allowing complete compromise of the affected device.

Critical Impact
Remote attackers can exploit this stack-based buffer overflow to execute arbitrary code on vulnerable D-Link DIR-816 routers, potentially gaining complete control of the device. This vulnerability affects end-of-life products that no longer receive security updates from D-Link.

Affected Products

D-Link DIR-816 Firmware version 1.10CNB05
D-Link DIR-816 Hardware

Discovery Timeline

June 5, 2025 - CVE-2025-5622 published to NVD
June 6, 2025 - Last updated in NVD database

Technical Details for CVE-2025-5622

Vulnerability Analysis

This vulnerability is classified as a stack-based buffer overflow (CWE-787: Out-of-bounds Write, CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the wirelessApcli_5g function, which handles wireless client configuration for the 5GHz band on affected D-Link routers.

The vulnerable endpoint /goform/wirelessApcli_5g accepts user-controlled input through multiple parameters without proper bounds checking. When processing the apcli_mode_5g, apcli_enc_5g, or apcli_default_key_5g parameters, the function fails to validate the length of input data before copying it to a fixed-size stack buffer. This allows an attacker to overflow the buffer and overwrite adjacent stack memory, including return addresses.

Successful exploitation could allow attackers to achieve arbitrary code execution with the privileges of the web server process, typically running as root on embedded devices. Given the device's network position as a router, compromise could enable network traffic interception, lateral movement, or use of the device in botnet operations.

Root Cause

The root cause is insufficient input validation in the wirelessApcli_5g function. The code fails to check the length of user-supplied strings for the apcli_mode_5g, apcli_enc_5g, and apcli_default_key_5g parameters before copying them into fixed-size stack buffers. This classic buffer overflow pattern allows attacker-controlled data to exceed buffer boundaries and corrupt adjacent stack memory.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An unauthenticated attacker can craft malicious HTTP POST requests to the /goform/wirelessApcli_5g endpoint containing oversized values in the vulnerable parameters. The attack does not require user interaction or prior authentication, making it particularly dangerous for devices exposed to the internet or accessible on local networks.

The vulnerability mechanism involves sending specially crafted requests to the affected endpoint. When the vulnerable function processes these oversized parameter values, it copies the attacker-controlled data into stack buffers without proper bounds validation, leading to memory corruption and potential code execution. For detailed technical analysis, refer to the GitHub Vulnerability Documentation.

Detection Methods for CVE-2025-5622

Indicators of Compromise

Unexpected HTTP POST requests to /goform/wirelessApcli_5g with abnormally long parameter values
Router crashes or reboots coinciding with web interface access attempts
Unusual outbound network connections from the router to unknown IP addresses
Modified router configurations or unexpected DNS settings

Detection Strategies

Monitor HTTP traffic to router management interfaces for POST requests targeting /goform/wirelessApcli_5g with parameter lengths exceeding normal operational values
Implement network intrusion detection rules to identify buffer overflow exploitation attempts against D-Link router endpoints
Deploy network segmentation to isolate management interfaces and log all access attempts
Review router logs for repeated authentication failures or abnormal access patterns

Monitoring Recommendations

Enable logging on all network devices and aggregate logs to a centralized SIEM for correlation analysis
Configure alerts for any external network access attempts to router management ports (typically 80, 443, 8080)
Regularly audit firmware versions across network infrastructure to identify end-of-life devices requiring replacement

How to Mitigate CVE-2025-5622

Immediate Actions Required

Disable remote web management access immediately on affected D-Link DIR-816 devices
Restrict access to the router's management interface to trusted internal IP addresses only using firewall rules
Consider replacing the affected device with a currently supported router model, as this product is end-of-life and will not receive security patches
Segment network traffic to isolate the vulnerable router from critical systems

Patch Information

No patch is available for this vulnerability. D-Link has confirmed that the DIR-816 firmware version 1.10CNB05 is end-of-life (EoL) and no longer supported. Devices running unsupported firmware will not receive security updates. D-Link recommends replacing affected devices with newer, supported models. For more information, visit the D-Link Official Website.

Additional vulnerability details are available through VulDB #311108.

Workarounds

Disable the web management interface entirely if not required for operations
Configure firewall rules to block all external access to the router's management ports
Place the vulnerable router behind a more secure network device that can filter malicious traffic
Enable MAC address filtering to restrict which devices can access the management interface

bash

# Example iptables rules to restrict management interface access
# Block external access to web management ports
iptables -A INPUT -p tcp --dport 80 -i eth0 -j DROP
iptables -A INPUT -p tcp --dport 443 -i eth0 -j DROP
iptables -A INPUT -p tcp --dport 8080 -i eth0 -j DROP

# Allow management access only from trusted internal IP
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT