CVE-2026-4486: D-Link DIR-513 Buffer Overflow Vulnerability

CVE-2026-4486 Overview

A stack-based buffer overflow vulnerability has been identified in D-Link DIR-513 wireless routers running firmware version 1.10. This vulnerability affects the formEasySetPassword function within the /goform/formEasySetPassword endpoint of the Web Service component. By manipulating the curTime argument, an attacker can trigger a stack-based buffer overflow condition that could lead to arbitrary code execution on affected devices.

Critical Impact

This vulnerability allows remote attackers with low-level privileges to exploit a stack-based buffer overflow in the router's web service, potentially achieving complete device compromise. The affected product has reached end-of-life and is no longer supported by D-Link.

Affected Products

• D-Link DIR-513 firmware version 1.10
• D-Link DIR-513 (all versions - end-of-life product)

Discovery Timeline

• March 20, 2026 - CVE-2026-4486 published to NVD
• March 24, 2026 - Last updated in NVD database

Technical Details for CVE-2026-4486

Vulnerability Analysis

This vulnerability falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), specifically manifesting as a stack-based buffer overflow. The vulnerable formEasySetPassword function fails to properly validate the length of data received through the curTime parameter before copying it to a fixed-size stack buffer.

The D-Link DIR-513 router's web service exposes the /goform/formEasySetPassword endpoint to handle password configuration requests. When processing incoming requests, the function reads the curTime argument without adequate bounds checking. An attacker can supply an oversized value that exceeds the allocated buffer space, causing memory corruption on the stack. This type of memory corruption can overwrite critical stack data including return addresses, potentially allowing the attacker to redirect program execution to attacker-controlled code.

Since this attack can be performed remotely over the network, any device with the web management interface exposed represents a potential target. The vulnerability is particularly concerning because the D-Link DIR-513 has been designated as end-of-life, meaning no security patches will be released to address this issue.

Root Cause

The root cause is the absence of proper input validation and boundary checking in the formEasySetPassword function when handling the curTime parameter. The function copies user-supplied data directly to a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity, resulting in a classic stack-based buffer overflow condition.

Attack Vector

The attack vector is network-based and requires the attacker to have low-level access privileges to the router's web interface. The exploitation flow involves:

1. The attacker identifies a D-Link DIR-513 router with the web service accessible over the network
2. A crafted HTTP request is sent to the /goform/formEasySetPassword endpoint
3. The malicious request contains an oversized curTime parameter designed to overflow the stack buffer
4. The overflow overwrites critical stack data, potentially including the return address
5. Upon function return, execution may be redirected to attacker-controlled memory locations

A proof-of-concept exploit has been publicly disclosed and is available for review. Technical documentation and a PoC script can be found in the GitHub PoC Documentation repository.

Detection Methods for CVE-2026-4486

Indicators of Compromise

• Unusual HTTP POST requests to /goform/formEasySetPassword with abnormally large curTime parameter values
• Web server crashes or unexpected reboots of the DIR-513 device
• Evidence of memory corruption in device logs (if available)
• Unexpected changes to device configuration or password settings

Detection Strategies

• Monitor network traffic for HTTP requests targeting /goform/formEasySetPassword with payload sizes exceeding normal operational parameters
• Implement intrusion detection signatures to identify buffer overflow attack patterns in web service requests
• Deploy network segmentation to isolate legacy IoT devices and monitor traffic at segment boundaries
• Review web server access logs for repeated requests to the vulnerable endpoint

Monitoring Recommendations

• Enable logging on all network perimeter devices to capture traffic to and from D-Link DIR-513 routers
• Configure SIEM rules to alert on anomalous POST request sizes to goform endpoints
• Implement network behavior analysis to detect exploitation attempts and subsequent post-compromise activity
• Regularly audit network inventory to identify any remaining DIR-513 devices in the environment

How to Mitigate CVE-2026-4486

Immediate Actions Required

• Replace D-Link DIR-513 devices with currently supported router models immediately, as no security patches will be released for this end-of-life product
• If immediate replacement is not possible, disable remote web management access and restrict the management interface to trusted internal networks only
• Implement network access controls to prevent untrusted users from reaching the router's web interface
• Segment the network to isolate vulnerable IoT devices from critical systems

Patch Information

This vulnerability affects the D-Link DIR-513, which has been designated as an end-of-life product by the manufacturer. D-Link has confirmed that no security updates will be provided for this device. The only reliable mitigation is to replace the affected hardware with a currently supported product. For more information about D-Link's product lifecycle, visit the D-Link Official Website.

Additional technical details and vulnerability tracking information are available at VulDB #352009 Entry.

Workarounds

• Disable the web management interface entirely if not required for operations
• Configure firewall rules to block external access to port 80/443 on the DIR-513 device
• Use VPN or other secure access methods if remote management is absolutely necessary, combined with strict access control lists
• Implement MAC address filtering and strong WPA3 encryption to limit who can connect to the network

# Firewall rule example to block external access to router management
# Apply at your perimeter firewall or upstream router
iptables -A FORWARD -d <DIR-513-IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <DIR-513-IP> -p tcp --dport 443 -j DROP