CVE-2025-50673: Dlink Di-8003 Buffer Overflow Vulnerability

CVE-2025-50673 Overview

CVE-2025-50673 is a buffer overflow vulnerability affecting D-Link DI-8003 routers running firmware version 16.07.26A1. The flaw resides in the /webgl.asp endpoint, which improperly handles the http_lanport parameter. An unauthenticated remote attacker can send a crafted HTTP request to trigger memory corruption and cause a denial-of-service condition on the device.

The vulnerability is classified under [CWE-120] (Buffer Copy without Checking Size of Input). It requires no privileges or user interaction and is exploitable over the network.

Critical Impact

Unauthenticated remote attackers can crash the D-Link DI-8003 router by sending a malformed http_lanport value to the /webgl.asp endpoint, disrupting network connectivity for all users behind the device.

Affected Products

• D-Link DI-8003 router (hardware)
• D-Link DI-8003 firmware version 16.07.26A1
• Deployments exposing the web management interface on the LAN or WAN

Discovery Timeline

• 2026-04-08 - CVE-2025-50673 published to the National Vulnerability Database (NVD)
• 2026-04-10 - Last updated in NVD database

Technical Details for CVE-2025-50673

Vulnerability Analysis

The DI-8003 web management interface exposes the /webgl.asp endpoint, which accepts user-supplied input through the http_lanport parameter. The handler copies the parameter value into a fixed-size stack buffer without validating its length. Supplying an oversized string causes the buffer to overflow adjacent memory regions, corrupting saved return addresses and control structures.

Exploitation does not require authentication. The attacker only needs network reachability to the device's HTTP management service. The impact is constrained to availability — the device crashes or reboots — without confirmed code execution or data disclosure under current public analysis.

The http_lanport parameter is intended to receive a numeric TCP port value. The absence of length checks and type validation allows arbitrary byte sequences to reach the vulnerable strcpy-style routine inside the ASP handler.

Root Cause

The root cause is the absence of bounds checking when processing the http_lanport query parameter. The web server binary copies the attacker-controlled value into a stack-allocated buffer of insufficient size. This pattern is consistent with [CWE-120], where input size is never compared against the destination buffer capacity before the copy operation.

Attack Vector

An attacker crafts an HTTP GET or POST request to /webgl.asp containing a long string in the http_lanport parameter. The request is sent directly to the router's management interface. When the request reaches the parameter parser, the oversized value overruns the destination buffer and crashes the web service or the underlying process, denying service to legitimate users.

The vulnerability manifests when the HTTP handler processes the parameter. No authentication challenge is presented before the parameter is parsed, allowing pre-auth exploitation. Refer to the GitHub IoT Vulnerability Collection for additional technical context.

Detection Methods for CVE-2025-50673

Indicators of Compromise

• HTTP requests to /webgl.asp containing unusually long http_lanport parameter values
• Repeated device reboots or web management interface crashes following inbound HTTP traffic
• Unexpected loss of LAN connectivity correlated with management plane access attempts
• Source IP addresses scanning multiple D-Link administrative endpoints in sequence

Detection Strategies

• Inspect web server access logs on the router for requests targeting /webgl.asp with http_lanport values exceeding expected port number length
• Deploy network IDS signatures that flag HTTP requests with oversized query string parameters directed at D-Link management interfaces
• Correlate device availability monitoring alerts with inbound HTTP traffic to the router's administrative port

Monitoring Recommendations

• Enable syslog forwarding from the DI-8003 to a centralized logging platform and alert on web service restart events
• Monitor for unauthenticated HTTP requests originating outside the trusted management network
• Track HTTP parameter length distributions against a baseline to identify anomalous values

How to Mitigate CVE-2025-50673

Immediate Actions Required

• Restrict access to the DI-8003 web management interface to trusted administrative networks only, blocking inbound HTTP/HTTPS from the WAN
• Disable remote management features if they are not required for operational use
• Apply firmware updates from D-Link as soon as a patched version becomes available
• Audit perimeter firewall rules to confirm the router's management port is not reachable from the public internet

Patch Information

No confirmed patched firmware version is listed in the public advisory at the time of NVD publication. Administrators should monitor the D-Link Security Bulletin for an official fix addressing CVE-2025-50673 and apply the update immediately upon release.

Workarounds

• Place the DI-8003 management interface behind a VPN or jump host accessible only to administrators
• Use access control lists on upstream switches or firewalls to limit which source IPs can reach the router's HTTP service
• Segment the device into a dedicated management VLAN with strict ingress filtering
• Replace the device with a supported model if firmware updates are not forthcoming

# Configuration example: restrict management access using iptables on an upstream Linux firewall
iptables -A FORWARD -p tcp -d <DI-8003_IP> --dport 80 -s <ADMIN_SUBNET> -j ACCEPT
iptables -A FORWARD -p tcp -d <DI-8003_IP> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <DI-8003_IP> --dport 443 -s <ADMIN_SUBNET> -j ACCEPT
iptables -A FORWARD -p tcp -d <DI-8003_IP> --dport 443 -j DROP