CVE-2025-70220: D-Link DIR-513 Buffer Overflow Flaw

CVE-2025-70220 Overview

A critical stack buffer overflow vulnerability has been identified in D-Link DIR-513 wireless routers running firmware version 1.10. The vulnerability exists in the goform/formAutoDetecWAN_wizard4 endpoint, where the curTime parameter is processed without adequate bounds checking. This flaw allows remote attackers to send specially crafted HTTP requests that overflow a stack-based buffer, potentially leading to arbitrary code execution on the affected device.

Critical Impact
This network-accessible vulnerability requires no authentication and can be exploited remotely to gain complete control over the affected D-Link router, potentially compromising the entire network segment.

Affected Products

D-Link DIR-513 firmware version 1.10

Discovery Timeline

2026-03-04 - CVE-2025-70220 published to NVD
2026-03-05 - Last updated in NVD database

Technical Details for CVE-2025-70220

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption vulnerability that occurs when data written to a buffer on the stack exceeds its allocated size. In the case of the D-Link DIR-513, the web interface's WAN auto-detection wizard functionality fails to properly validate the length of user-supplied input in the curTime parameter before copying it to a fixed-size stack buffer.

The exploitation potential is significant as the vulnerable endpoint is accessible over the network without requiring prior authentication. An attacker can craft malicious HTTP POST requests containing an oversized curTime parameter value, causing the overflow condition. Successful exploitation overwrites adjacent stack memory, including the return address, enabling attackers to redirect program execution to attacker-controlled code.

Root Cause

The root cause of this vulnerability stems from unsafe string handling in the router's web server component. When processing the curTime parameter submitted to goform/formAutoDetecWAN_wizard4, the firmware uses a vulnerable copy operation (likely strcpy or sprintf) that does not enforce bounds checking. The destination buffer on the stack has a fixed allocation, but no validation occurs to ensure the input data fits within this allocation before the copy operation executes.

Attack Vector

The attack vector is network-based, requiring the attacker to have network access to the router's web management interface. Exploitation follows this general pattern:

The attacker identifies a vulnerable D-Link DIR-513 router on the network
A crafted HTTP POST request is sent to the /goform/formAutoDetecWAN_wizard4 endpoint
The request includes an oversized curTime parameter designed to overflow the stack buffer
The overflow overwrites the saved return address on the stack
When the function returns, execution transfers to attacker-controlled memory containing shellcode

The vulnerability is particularly dangerous because it requires no authentication, no user interaction, and can be exploited remotely from the local network or potentially from the internet if the management interface is exposed.

Detection Methods for CVE-2025-70220

Indicators of Compromise

Unusual or malformed HTTP POST requests to /goform/formAutoDetecWAN_wizard4 with abnormally long curTime parameter values
Router crashes, unexpected reboots, or unresponsive web interface indicating potential exploitation attempts
Unauthorized configuration changes or new administrative accounts on the router
Suspicious outbound network traffic from the router to unknown external hosts

Detection Strategies

Monitor network traffic for HTTP requests to D-Link router endpoints containing unusually large parameter values (typically exceeding 1KB for the curTime field)
Implement network-based intrusion detection rules to identify buffer overflow exploitation patterns targeting embedded device web interfaces
Deploy network segmentation and monitoring to detect any anomalous traffic patterns from IoT and router devices

Monitoring Recommendations

Enable logging on network firewalls and intrusion detection systems to capture traffic to router management interfaces
Regularly audit router configurations for unauthorized changes that may indicate successful compromise
Monitor for firmware version changes or unexpected device behavior that could signal exploitation

How to Mitigate CVE-2025-70220

Immediate Actions Required

Restrict access to the router's web management interface to trusted networks and IP addresses only
Disable remote management features if not required for operations
Check the D-Link Security Bulletin for available firmware updates addressing this vulnerability
Consider network segmentation to isolate vulnerable devices from critical network assets

Patch Information

Organizations should monitor D-Link's official security resources for firmware updates addressing this vulnerability. Review the D-Link Product Information page for the DIR-513 model for any available patches. Additional technical details about this vulnerability can be found in the GitHub CVE Report.

Workarounds

Configure firewall rules to restrict access to the router's management interface (TCP/80, TCP/443) to authorized management stations only
If possible, disable the WAN auto-detection wizard functionality to remove the vulnerable endpoint from exposure
Place the router behind an additional network security device that can filter malicious requests
Consider replacing end-of-life devices that may not receive security updates

bash

# Example iptables rules to restrict management access (apply on upstream firewall)
# Block external access to router management interface
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP

# Allow management only from trusted admin workstation
iptables -I FORWARD -s <ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s <ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 443 -j ACCEPT