CVE-2025-50644: D-Link DI-8003 Buffer Overflow Vulnerability

CVE-2025-50644 Overview

CVE-2025-50644 is a buffer overflow vulnerability affecting the D-Link DI-8003 router running firmware version 16.07.26A1. The flaw resides in the qj.asp endpoint, which fails to properly validate user-supplied input before copying it into a fixed-size buffer [CWE-120]. Remote attackers can trigger the condition over the network without authentication or user interaction. Successful exploitation causes the device to crash, resulting in denial of service on the affected router.

Critical Impact

Unauthenticated network attackers can send crafted requests to the qj.asp endpoint and force a buffer overflow that disrupts router availability.

Affected Products

• D-Link DI-8003 hardware appliance
• D-Link DI-8003 firmware version 16.07.26A1
• Deployments exposing the web management interface to untrusted networks

Discovery Timeline

• 2026-04-08 - CVE-2025-50644 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2025-50644

Vulnerability Analysis

The vulnerability stems from improper input validation in the qj.asp endpoint of the DI-8003 web management interface. The endpoint accepts user-controlled parameters and copies them into a fixed-size stack or heap buffer without enforcing length boundaries. When the supplied data exceeds the expected size, adjacent memory is overwritten and the affected process crashes.

The issue is classified under CWE-120: Buffer Copy without Checking Size of Input. The advertised impact is limited to availability, with no confidentiality or integrity compromise documented by the vendor. The router becomes unresponsive until restarted, which interrupts all network services dependent on the device.

Root Cause

The qj.asp handler uses unbounded copy operations on parameters received in HTTP requests. The firmware does not enforce length checks, sanitize input, or apply stack canaries that would catch the overrun before it corrupts execution state. This pattern is common in embedded ASP-style CGI handlers in consumer and small-business networking equipment.

Attack Vector

The attack is remote and unauthenticated. An attacker sends a crafted HTTP request containing an oversized parameter value to the qj.asp endpoint on the router management interface. The overflow corrupts memory and the device service terminates, producing a denial-of-service condition. No specialized tooling is required beyond standard HTTP request crafting.

No public proof-of-concept exploit is currently listed in the references, and the issue is not present on the CISA Known Exploited Vulnerabilities catalog. Technical details are referenced in the GitHub IoT Vulnerability Collection and the D-Link Security Advisory SAP10505.

Detection Methods for CVE-2025-50644

Indicators of Compromise

• Unexpected reboots, watchdog resets, or service crashes on D-Link DI-8003 routers running firmware 16.07.26A1.
• HTTP requests to /qj.asp containing abnormally long parameter values originating from untrusted sources.
• Loss of management plane connectivity coinciding with inbound HTTP traffic to the device.

Detection Strategies

• Inspect web access logs and network captures for POST or GET requests targeting qj.asp with parameter lengths exceeding normal application use.
• Deploy network IDS rules that flag oversized HTTP parameters destined for DI-8003 management interfaces.
• Correlate device unavailability events with preceding HTTP traffic to identify probable exploitation attempts.

Monitoring Recommendations

• Forward router syslog and crash telemetry to a centralized logging platform for alerting on repeated service restarts.
• Monitor north-south traffic to the router management VLAN and alert on any external sources reaching the admin interface.
• Track firmware version inventory across deployed DI-8003 units to confirm patch coverage over time.

How to Mitigate CVE-2025-50644

Immediate Actions Required

• Restrict access to the DI-8003 web management interface to trusted administrative networks using ACLs or firewall rules.
• Disable WAN-side management access if it is currently enabled on affected devices.
• Apply firmware updates published by D-Link as soon as they are available for the DI-8003 platform.

Patch Information

Review the D-Link Security Advisory SAP10505 and the general D-Link Security Bulletin for vendor-supplied firmware updates and remediation guidance. Verify the running firmware version after upgrade and confirm it is later than 16.07.26A1.

Workarounds

• Place the router management interface on an isolated VLAN reachable only by administrative jump hosts.
• Block inbound HTTP and HTTPS requests to qj.asp at an upstream firewall or reverse proxy where feasible.
• Replace end-of-support DI-8003 devices with currently supported hardware if no patch is available for the deployed firmware branch.

# Example: restrict router management access at an upstream firewall
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP