CVE-2025-70243: D-Link DIR-513 Buffer Overflow Flaw

CVE-2025-70243 Overview

A stack buffer overflow vulnerability has been identified in the D-Link DIR-513 router firmware version 1.10. The vulnerability exists in the web management interface, specifically within the goform/formSetWAN_Wizard534 endpoint. An attacker can exploit this flaw by sending a maliciously crafted curTime parameter to the vulnerable endpoint, triggering a stack-based buffer overflow condition that can result in denial of service.

Critical Impact

This network-accessible vulnerability allows unauthenticated remote attackers to crash affected D-Link DIR-513 routers by exploiting a stack buffer overflow, 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

• 2026-03-09 - CVE CVE-2025-70243 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2025-70243

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption vulnerability that occurs when a program writes data beyond the boundaries of a fixed-length buffer allocated on the stack. In the context of the D-Link DIR-513 router, the web management interface fails to properly validate the length of user-supplied input in the curTime parameter before copying it to a stack-allocated buffer.

The affected endpoint goform/formSetWAN_Wizard534 is part of the router's WAN setup wizard functionality. When processing HTTP requests to this endpoint, the firmware does not implement adequate bounds checking on the curTime parameter, allowing an attacker to supply an oversized input that overwrites adjacent memory on the stack.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the firmware's HTTP request handler. The curTime parameter is processed without proper length checks before being copied into a fixed-size stack buffer. This lack of boundary validation is a common issue in embedded device firmware, particularly in legacy devices where memory-safe programming practices may not have been consistently applied during development.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker with network access to the router's web management interface can send a specially crafted HTTP POST request to the goform/formSetWAN_Wizard534 endpoint. By including an excessively long curTime parameter value, the attacker can trigger the buffer overflow condition.

The exploitation is straightforward:

1. The attacker identifies a vulnerable D-Link DIR-513 router with firmware version 1.10
2. A malicious HTTP POST request is crafted targeting the goform/formSetWAN_Wizard534 endpoint
3. The curTime parameter is populated with data exceeding the expected buffer size
4. When processed, the oversized input overflows the stack buffer, corrupting adjacent memory
5. This memory corruption leads to denial of service through application crash

For technical details on the vulnerability, refer to the GitHub CVE Report.

Detection Methods for CVE-2025-70243

Indicators of Compromise

• Unexpected router reboots or unresponsive web management interface
• Anomalous HTTP POST requests to /goform/formSetWAN_Wizard534 with unusually large curTime parameter values
• Network traffic patterns showing repeated attempts to access the WAN wizard endpoint
• Router crash logs indicating memory access violations or segmentation faults

Detection Strategies

• Monitor network traffic for HTTP POST requests targeting goform/formSetWAN_Wizard534 with payload sizes exceeding normal operational parameters
• Implement network intrusion detection rules to identify oversized parameters in requests to D-Link router management interfaces
• Deploy web application firewall rules to block requests with excessively long parameter values to router management endpoints
• Review router access logs for unusual patterns of requests to the WAN wizard functionality

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for traffic to D-Link router management ports
• Configure alerts for router availability issues that may indicate successful exploitation
• Implement network segmentation to limit exposure of router management interfaces
• Monitor for reconnaissance activity targeting D-Link device management endpoints

How to Mitigate CVE-2025-70243

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required for operational purposes
• Implement network segmentation to isolate the router management interface from untrusted networks
• Consider deploying a firewall rule to block external access to the /goform/ endpoints

Patch Information

D-Link users should consult the D-Link Security Bulletin for official patch availability and firmware update instructions. Check the D-Link Product Information page for the latest firmware releases for the DIR-513 router.

Given that the DIR-513 may be an end-of-life product, users should verify whether continued support is available. If no patch is forthcoming, consider replacing the device with a currently supported model.

Workarounds

• Configure access control lists (ACLs) on the router to restrict management interface access to specific trusted IP addresses
• Disable the web management interface entirely and use alternative configuration methods if available
• Place the router behind an additional firewall that can filter malicious requests
• If the device must remain in production without a patch, implement strict network monitoring and access controls

# Example iptables rule to restrict access to router management interface
# Apply on upstream firewall or gateway device
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 only from trusted management subnet
iptables -I FORWARD -s 192.168.1.0/24 -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT