CVE-2025-70237: D-Link DIR-513 Buffer Overflow Flaw

CVE-2025-70237 Overview

A critical stack buffer overflow vulnerability has been identified in D-Link DIR-513 router firmware version 1.10. The vulnerability exists in the goform/formSetPortTr endpoint, where improper handling of the curTime parameter allows attackers to overflow a stack-based buffer. This memory corruption flaw can be exploited remotely without authentication, potentially leading to complete device compromise, arbitrary code execution, or denial of service conditions on affected routers.

Critical Impact

Unauthenticated remote attackers can exploit this stack buffer overflow to execute arbitrary code on affected D-Link DIR-513 routers, potentially gaining full control of the network device.

Affected Products

• D-Link DIR-513 Firmware version 1.10
• D-Link DIR-513 Hardware (all revisions running vulnerable firmware)

Discovery Timeline

• 2026-03-03 - CVE-2025-70237 published to NVD
• 2026-03-04 - Last updated in NVD database

Technical Details for CVE-2025-70237

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), specifically manifesting as a stack buffer overflow in the D-Link DIR-513 router's web management interface. The vulnerable endpoint goform/formSetPortTr fails to properly validate the length of input supplied via the curTime parameter before copying it to a fixed-size stack buffer.

When an attacker sends an HTTP request with an oversized curTime parameter value to the vulnerable endpoint, the application copies the user-supplied data into a stack-allocated buffer without adequate bounds checking. This allows the attacker to overwrite adjacent stack memory, including saved return addresses and other critical control flow data.

The network-accessible nature of this vulnerability is particularly concerning as it requires no authentication and no user interaction to exploit. Attackers can send malicious requests directly to the router's web interface, making this an ideal target for automated exploitation and botnet recruitment campaigns targeting consumer networking equipment.

Root Cause

The root cause of this vulnerability is insufficient input validation in the firmware's web server component. The curTime parameter handler in the formSetPortTr form processor uses an unsafe string copy operation that does not verify the input length against the destination buffer's capacity. This classic buffer overflow pattern allows attackers to write beyond the allocated stack memory region, corrupting adjacent stack frames and potentially hijacking program execution.

Attack Vector

The attack can be executed remotely over the network by sending a specially crafted HTTP POST request to the goform/formSetPortTr endpoint on the router's web management interface (typically accessible on port 80 or 443). The attacker supplies an oversized value for the curTime parameter, which triggers the buffer overflow condition.

A successful exploit would involve:

1. Identifying a vulnerable D-Link DIR-513 router on the network
2. Crafting an HTTP POST request targeting the goform/formSetPortTr endpoint
3. Including an oversized curTime parameter designed to overflow the stack buffer
4. Overwriting the return address with a value pointing to attacker-controlled shellcode or ROP gadgets
5. Achieving arbitrary code execution with the privileges of the web server process (typically root on embedded devices)

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

Detection Methods for CVE-2025-70237

Indicators of Compromise

• Unusually large HTTP POST requests to /goform/formSetPortTr endpoint on D-Link DIR-513 devices
• Abnormal curTime parameter values exceeding typical timestamp lengths (more than 50-100 characters)
• Router instability, unexpected reboots, or unresponsive web management interface
• Unexpected outbound network connections from the router to unknown external hosts
• Modified router configuration or unauthorized administrative accounts

Detection Strategies

• Deploy network intrusion detection rules to identify HTTP requests with oversized curTime parameters targeting D-Link router endpoints
• Monitor HTTP traffic to /goform/formSetPortTr for anomalous request patterns or payload sizes
• Implement web application firewall rules to block requests with excessively long parameter values to D-Link device management interfaces
• Configure alerts for repeated failed or malformed requests to router administration endpoints

Monitoring Recommendations

• Enable logging on network firewalls and capture traffic to/from D-Link DIR-513 management interfaces
• Monitor for firmware integrity changes or unauthorized modifications to router configurations
• Track DNS queries and outbound connections from router IP addresses for signs of compromise
• Establish baseline network behavior for IoT devices and alert on deviations

How to Mitigate CVE-2025-70237

Immediate Actions Required

• Check the D-Link Security Bulletin for available firmware updates addressing this vulnerability
• Restrict access to the router's web management interface to trusted networks only
• Disable remote management features if not required for operations
• Place vulnerable routers behind network firewalls with strict ingress filtering
• Consider replacing end-of-life devices that may not receive security patches

Patch Information

D-Link has been notified of this vulnerability. Users should monitor the D-Link Security Bulletin for official patches and firmware updates. Check the D-Link Product Information page for the latest available firmware version for the DIR-513.

Given that the DIR-513 is an older device model, verify with D-Link whether the device is still within its support lifecycle and eligible for security updates.

Workarounds

• Disable the web management interface entirely if not actively used for administration
• Configure firewall rules to block external access to ports 80 and 443 on the router's management interface
• Use VPN or out-of-band management for router administration to limit attack surface exposure
• Implement network segmentation to isolate vulnerable IoT devices from critical network assets
• Monitor for and block suspicious HTTP POST requests with abnormally large parameter values

# Example iptables rules to restrict management interface access
# Block external access to router management ports
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

# Log potential exploit attempts targeting the vulnerable endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "formSetPortTr" --algo bm -j LOG --log-prefix "DIR513-EXPLOIT: "