CVE-2025-70242: D-Link DIR-513 Buffer Overflow Vulnerability

CVE-2025-70242 Overview

A stack buffer overflow vulnerability exists in D-Link DIR-513 firmware version 1.10. The vulnerability is triggered via the webPage parameter when processing requests to the goform/formSetWanPPTP endpoint. This flaw allows remote attackers to cause a denial of service condition by sending specially crafted requests to the affected router's web management interface.

Critical Impact
Network-accessible stack buffer overflow in D-Link DIR-513 routers can lead to denial of service, potentially disrupting network connectivity for all connected devices.

Affected Products

D-Link DIR-513 Firmware version 1.10
D-Link DIR-513 Hardware

Discovery Timeline

2026-03-10 - CVE CVE-2025-70242 published to NVD
2026-03-11 - Last updated in NVD database

Technical Details for CVE-2025-70242

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when user-supplied input exceeds the allocated buffer size on the stack. The affected endpoint goform/formSetWanPPTP handles WAN PPTP configuration settings and fails to properly validate the length of the webPage parameter before copying it to a fixed-size stack buffer.

When an attacker submits an oversized value for the webPage parameter, the input overflows the allocated buffer space, corrupting adjacent stack memory. This memory corruption can overwrite critical stack data including return addresses and saved registers, leading to unpredictable behavior and service disruption.

Root Cause

The root cause of this vulnerability is improper input validation in the web form handler for PPTP WAN configuration. The firmware does not implement adequate bounds checking on the webPage parameter before copying user-supplied data into a stack-allocated buffer. This allows attackers to provide input that exceeds the buffer's capacity, resulting in a classic stack buffer overflow condition.

Attack Vector

The vulnerability is exploitable remotely over the network without requiring authentication or user interaction. An attacker can send a malicious HTTP POST request to the goform/formSetWanPPTP endpoint with an oversized webPage parameter value. The attack targets the router's web management interface, which is typically accessible on the local network and potentially exposed to the internet if remote management is enabled.

The exploitation process involves:

Identifying a vulnerable D-Link DIR-513 router running firmware version 1.10
Crafting an HTTP POST request to the /goform/formSetWanPPTP endpoint
Including an excessively long string in the webPage parameter to trigger the overflow
The overflow corrupts stack memory, causing the web service or device to crash

For detailed technical analysis and proof-of-concept information, refer to the GitHub CVE-Report Repository.

Detection Methods for CVE-2025-70242

Indicators of Compromise

Unexpected router reboots or web interface unavailability
Abnormally large HTTP POST requests to /goform/formSetWanPPTP endpoint
Network logs showing repeated requests with oversized webPage parameter values
Router crash dumps or system instability reports

Detection Strategies

Monitor HTTP traffic to router management interfaces for unusually large POST requests
Implement intrusion detection rules to flag requests containing oversized parameters to formSetWanPPTP
Configure network monitoring to alert on repeated connection attempts to router web interfaces from unusual sources
Deploy web application firewall rules to limit parameter sizes for router management endpoints

Monitoring Recommendations

Enable logging on network firewalls to capture traffic destined for router management ports
Review router access logs for suspicious POST requests to goform endpoints
Set up automated alerts for router availability monitoring to detect DoS conditions
Audit network segmentation to ensure router management interfaces are not exposed to untrusted networks

How to Mitigate CVE-2025-70242

Immediate Actions Required

Restrict access to the router's web management interface to trusted IP addresses only
Disable remote management if not required
Implement network segmentation to isolate router management interfaces from untrusted networks
Monitor for firmware updates from D-Link and apply patches when available

Patch Information

D-Link has been notified of this vulnerability. Users should monitor the D-Link Security Bulletin page for official patches and security advisories. Until a patch is available, implement the recommended workarounds to reduce exposure.

For additional product information, visit the D-Link Product Information page.

Workarounds

Configure firewall rules to block external access to the router's web management interface (typically port 80/443)
Use access control lists (ACLs) to limit management access to specific trusted IP addresses
Disable WAN-side management access through the router's configuration interface
Consider replacing end-of-life devices with supported models that receive regular security updates

bash

# Example firewall rule to restrict router management access
# Adjust IP ranges and ports according to your network configuration
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP