CVE-2026-6014: D-Link DIR-513 Buffer Overflow Vulnerability

CVE-2026-6014 Overview

A buffer overflow vulnerability has been identified in D-Link DIR-513 firmware version 1.10. This security flaw affects the formAdvanceSetup function within the /goform/formAdvanceSetup component of the POST Request Handler. By manipulating the webpage argument, a remote attacker can trigger a buffer overflow condition, potentially leading to arbitrary code execution or denial of service on the affected device.

Critical Impact

This vulnerability affects end-of-life D-Link DIR-513 routers that are no longer receiving security updates, leaving devices permanently vulnerable to remote exploitation via network-based attacks.

Affected Products

• D-Link DIR-513 Firmware Version 1.10
• D-Link DIR-513 devices running affected POST Request Handler component
• Legacy D-Link DIR-513 deployments (end-of-life product)

Discovery Timeline

• 2026-04-10 - CVE-2026-6014 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-6014

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the formAdvanceSetup function, which handles HTTP POST requests submitted to the /goform/formAdvanceSetup endpoint on the router's web management interface.

The function fails to properly validate the length of the webpage parameter before copying its contents into a fixed-size memory buffer. When an attacker supplies an overly long string for the webpage argument, the function writes beyond the allocated buffer boundaries, corrupting adjacent memory regions.

The vulnerability is remotely exploitable over the network, requiring only low-privilege authentication to the device's web interface. No user interaction is necessary beyond initial authentication, making this a significant threat to exposed devices.

Root Cause

The root cause of CVE-2026-6014 is inadequate input validation in the formAdvanceSetup function. The function processes the webpage parameter from incoming POST requests without performing proper bounds checking before memory copy operations. This classic buffer overflow pattern occurs when user-controlled input length exceeds the statically allocated buffer size, allowing memory corruption.

Attack Vector

The attack can be initiated remotely over the network. An authenticated attacker can craft a malicious HTTP POST request to the /goform/formAdvanceSetup endpoint with an oversized webpage parameter value. The vulnerability is exploitable with low attack complexity and requires no user interaction beyond the initial malicious request.

The attacker sends a specially crafted POST request to the vulnerable endpoint. The formAdvanceSetup function receives the malicious webpage parameter and attempts to copy it into a fixed-size stack or heap buffer. Due to insufficient bounds checking, the oversized input overwrites adjacent memory, potentially allowing the attacker to hijack program execution flow or crash the device. Technical details regarding this vulnerability have been documented in the VulDB Vulnerability Entry #356570 and the Notion Setup Guide.

Detection Methods for CVE-2026-6014

Indicators of Compromise

• Abnormal HTTP POST requests to /goform/formAdvanceSetup with unusually large webpage parameter values
• Device crashes, reboots, or unresponsive web management interface following POST requests
• Unexpected network traffic patterns originating from D-Link DIR-513 devices
• Memory corruption artifacts or kernel panic logs on affected devices

Detection Strategies

• Implement network intrusion detection rules to monitor for oversized HTTP POST parameters targeting D-Link router endpoints
• Deploy web application firewall (WAF) rules to block requests to /goform/formAdvanceSetup with abnormal parameter lengths
• Monitor network logs for repeated authentication attempts followed by POST requests to /goform/ paths
• Use SentinelOne Singularity to detect exploitation attempts and anomalous network behavior from IoT devices

Monitoring Recommendations

• Enable comprehensive logging on network perimeter devices to capture traffic destined for D-Link router management interfaces
• Implement network segmentation to isolate legacy and end-of-life IoT devices from critical network segments
• Deploy continuous asset discovery to identify vulnerable D-Link DIR-513 devices across the network environment

How to Mitigate CVE-2026-6014

Immediate Actions Required

• Identify and inventory all D-Link DIR-513 devices running firmware version 1.10 within the network environment
• Restrict network access to the device's web management interface using firewall rules or access control lists
• Disable remote management functionality if not operationally required
• Plan for device replacement given the end-of-life status and lack of vendor support

Patch Information

This vulnerability affects D-Link DIR-513 devices that have reached end-of-life status and are no longer supported by the vendor. D-Link has discontinued security updates for this product line, meaning no official patch will be released. Organizations must consider device replacement as the only permanent remediation strategy. For additional information, visit the D-Link Official Website.

Workarounds

• Implement strict network access controls to limit who can reach the router's web management interface (management VLAN, IP allowlisting)
• Disable WAN-side remote management to prevent external exploitation
• Deploy a network firewall or reverse proxy to filter and inspect traffic destined for the vulnerable endpoint
• Replace affected D-Link DIR-513 devices with currently supported router models that receive ongoing security updates

# Configuration example - Network access restriction via iptables
# Block external access to router management interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

# Alternatively, restrict to specific management workstations
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP