CVE-2025-50666: D-Link DI-8003 Buffer Overflow Vulnerability

CVE-2025-50666 Overview

CVE-2025-50666 is a buffer overflow vulnerability in the D-Link DI-8003 router running firmware version 16.07.26A1. The flaw resides in the /web_post.asp endpoint, which improperly handles several user-supplied parameters. An unauthenticated attacker can trigger the overflow by sending a crafted HTTP GET request containing oversized values in parameters such as name, en, user_id, log, and time. Successful exploitation causes a denial-of-service condition on the affected device. The vulnerability is classified under [CWE-120] (Buffer Copy without Checking Size of Input).

Critical Impact

Unauthenticated remote attackers can crash D-Link DI-8003 devices by sending crafted HTTP GET requests to /web_post.asp, disrupting network connectivity for all downstream users.

Affected Products

• D-Link DI-8003 router (hardware)
• D-Link DI-8003 firmware version 16.07.26A1
• Deployments exposing the web management interface over reachable networks

Discovery Timeline

• 2026-04-08 - CVE-2025-50666 published to the National Vulnerability Database
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2025-50666

Vulnerability Analysis

The DI-8003 web management interface exposes the /web_post.asp handler, which processes multiple parameters supplied in HTTP GET requests. The handler copies attacker-controlled values into fixed-size stack or heap buffers without validating input length. When the supplied data exceeds the destination buffer, adjacent memory is overwritten, corrupting program state and crashing the web server process or the underlying device. The integrity and confidentiality of data on the device are not directly affected, but availability of the router and the network segments it serves is lost until reboot.

Root Cause

The root cause is the absence of bounds checking on parameters parsed from the HTTP request inside /web_post.asp. Functions in the request handler likely use unsafe string operations such as strcpy or sprintf on attacker-controlled values for name, en, user_id, log, and time. Without length validation, oversized inputs corrupt the call stack or heap metadata.

Attack Vector

The vulnerability is exploitable over the network with no authentication and no user interaction. An attacker who can reach the router's HTTP management interface, whether on the LAN or through an exposed WAN interface, sends a single crafted GET request to /web_post.asp with one or more oversized parameter values. The web service crashes, and on many embedded devices the watchdog forces a full reboot.

No verified public proof-of-concept code is available. Technical details are referenced in the GitHub IoT Vulnerability Collection and the D-Link Security Advisory SAP10505.

Detection Methods for CVE-2025-50666

Indicators of Compromise

• HTTP GET requests directed at /web_post.asp containing unusually long values for the name, en, user_id, log, or time parameters.
• Repeated, unexpected reboots or web service crashes on DI-8003 devices coinciding with inbound HTTP traffic.
• Sudden loss of management plane availability on the router while the data plane remains briefly responsive.

Detection Strategies

• Inspect HTTP request logs from the router or upstream proxies for /web_post.asp requests where parameter values exceed expected lengths (for example, more than 128 bytes).
• Deploy IDS or IPS signatures that flag GET requests to /web_post.asp containing parameter values above a defined byte threshold.
• Correlate router uptime resets with inbound HTTP traffic patterns in network telemetry.

Monitoring Recommendations

• Forward router syslog and SNMP trap data to a centralized log platform and alert on repeated process crashes or reboots.
• Monitor north-south traffic for unsolicited connections to the router's HTTP management port from untrusted sources.
• Track availability of the DI-8003 management interface with synthetic health checks to identify exploitation-driven outages.

How to Mitigate CVE-2025-50666

Immediate Actions Required

• Restrict access to the DI-8003 web administration interface to trusted management VLANs or specific administrative hosts.
• Disable WAN-side access to the HTTP management service if it is not strictly required.
• Review the D-Link Security Bulletin and D-Link Security Advisory SAP10505 for vendor-supplied firmware updates.

Patch Information

D-Link maintains security advisories for the DI-8003 series on its support portal. Administrators should consult the D-Link Security Advisory SAP10505 for the latest patched firmware release addressing CVE-2025-50666 and apply it to all affected devices running 16.07.26A1.

Workarounds

• Place the router's management interface behind a network ACL that permits only specific administrator source IPs.
• Block external HTTP requests to /web_post.asp at an upstream firewall or web filter until firmware is updated.
• If feasible, replace the device with a model that receives active security maintenance when no patch is available for the deployed firmware.

# Example: restrict access to the DI-8003 management interface with iptables on an upstream gateway
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