CVE-2025-46108: D-Link DIR-513 Buffer Overflow Flaw

CVE-2025-46108 Overview

A critical buffer overflow vulnerability has been discovered in D-Link DIR-513 routers running firmware version A1FW110. The vulnerability exists within the formTcpipSetup function, which handles TCP/IP configuration requests. Due to improper input validation, an attacker can send specially crafted requests to the affected function, potentially leading to memory corruption and arbitrary code execution on the device.

Critical Impact

This vulnerability allows remote attackers to execute arbitrary code on affected D-Link DIR-513 routers without authentication, potentially leading to complete device compromise, network infiltration, and malicious firmware modifications.

Affected Products

• D-Link DIR-513 Router
• D-Link DIR-513 Firmware Version A1FW110
• D-Link DIR-513 A1 Hardware Revision

Discovery Timeline

• 2026-03-04 - CVE-2025-46108 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2025-46108

Vulnerability Analysis

The vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The formTcpipSetup function in the D-Link DIR-513 router firmware fails to properly validate the length of user-supplied input before copying it to a fixed-size buffer in memory.

When processing TCP/IP configuration requests, the function accepts parameters from HTTP requests and copies them directly into stack or heap-allocated buffers without adequate bounds checking. This allows an attacker to supply input that exceeds the buffer's allocated size, overwriting adjacent memory regions including return addresses, function pointers, or other critical data structures.

The network-accessible nature of this vulnerability is particularly concerning as it does not require authentication, allowing any attacker with network access to the router's management interface to exploit it. Successful exploitation could result in complete confidentiality, integrity, and availability compromise of the affected device.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formTcpipSetup function. The firmware developers failed to implement proper bounds checking when handling user-supplied parameters related to TCP/IP configuration. Standard C library functions such as strcpy(), sprintf(), or similar unsafe memory copy operations may be used without first verifying that the destination buffer can accommodate the incoming data. This is a common pattern in embedded device firmware where security controls are often minimized due to resource constraints.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by sending a malicious HTTP POST request to the router's web management interface targeting the formTcpipSetup endpoint. The payload would include oversized parameters designed to overflow the vulnerable buffer, allowing the attacker to:

1. Crash the device - Causing a denial of service by corrupting critical memory structures
2. Execute arbitrary code - By overwriting return addresses or function pointers with attacker-controlled values
3. Gain persistent access - By modifying firmware or configuration to maintain access after device reboot

The vulnerability is exploitable from the local network by default. If the device's web management interface is exposed to the internet through port forwarding or misconfiguration, remote exploitation becomes possible.

For technical details and proof-of-concept information, see the GitHub CVE-2025-46108 Report and the GitHub PoC for DIR-513.

Detection Methods for CVE-2025-46108

Indicators of Compromise

• Unexpected router reboots or crashes indicating potential exploitation attempts
• Unusual HTTP POST requests to the router's management interface targeting TCP/IP configuration endpoints
• Modified router configuration settings that were not authorized by administrators
• Unexpected outbound network connections originating from the router
• Changes to firmware or persistent storage on the device

Detection Strategies

• Monitor network traffic for oversized HTTP POST requests to the router's web interface, particularly those targeting /goform/formTcpipSetup or similar endpoints
• Implement intrusion detection rules to identify buffer overflow patterns in traffic destined for the router's management ports (typically port 80 or 443)
• Deploy network segmentation to isolate vulnerable routers and enable logging of all access attempts
• Configure SIEM alerts for repeated failed requests or unusual traffic patterns targeting router management interfaces

Monitoring Recommendations

• Enable logging on all network segments containing D-Link DIR-513 devices
• Monitor for anomalous HTTP traffic patterns to router management interfaces
• Implement network-level monitoring to detect exploitation attempts before they reach vulnerable devices
• Regularly audit router configurations for unauthorized changes that may indicate compromise

How to Mitigate CVE-2025-46108

Immediate Actions Required

• Disable remote management access on affected D-Link DIR-513 routers immediately
• Restrict access to the router's web management interface to trusted IP addresses only
• Implement firewall rules to block external access to the router's management ports
• Consider replacing affected devices with actively supported hardware if no patch is available
• Monitor the D-Link Security Bulletin for firmware updates

Patch Information

At the time of this publication, check the D-Link Security Bulletin for the latest security advisories and firmware updates for the DIR-513. Given the end-of-life status of many older D-Link devices, a firmware patch may not be available. Organizations should verify support status and consider device replacement if the affected product is no longer receiving security updates.

Workarounds

• Disable the web management interface entirely if not required for operations
• Implement network segmentation to isolate affected routers from untrusted networks
• Use a VPN or jump host architecture to access router management interfaces rather than direct access
• Apply strict access control lists (ACLs) at the network perimeter to prevent unauthorized access to management services
• Consider deploying a web application firewall (WAF) in front of the management interface to filter malicious requests

# Example: Restrict management access via iptables 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 only trusted management workstation
iptables -I FORWARD -s <TRUSTED_ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT