CVE-2025-45059: D-Link DI-8300 Buffer Overflow DoS Flaw

CVE-2025-45059 Overview

A buffer overflow vulnerability has been identified in the D-Link DI-8300 router firmware version 16.07.26A1. The vulnerability exists in the tgfile_htm function, which improperly handles the fn parameter, allowing attackers to overflow a buffer with crafted input. This firmware vulnerability affects the device's web management interface and can be exploited to cause a Denial of Service (DoS) condition.

Critical Impact

Attackers can exploit this buffer overflow to crash the affected D-Link DI-8300 router, disrupting network connectivity for all connected devices and potentially affecting business operations dependent on the network infrastructure.

Affected Products

• D-Link DI-8300 firmware version 16.07.26A1
• D-Link DI-8300 routers running vulnerable firmware versions

Discovery Timeline

• 2026-04-08 - CVE-2025-45059 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2025-45059

Vulnerability Analysis

This vulnerability represents a classic buffer overflow condition in embedded router firmware. The tgfile_htm function within the D-Link DI-8300's web management interface fails to properly validate the length of user-supplied data passed through the fn parameter before copying it into a fixed-size buffer.

When processing requests to the affected function, the firmware allocates a buffer of predetermined size to store the fn parameter value. However, the code does not implement proper bounds checking, allowing an attacker to supply input that exceeds the buffer's allocated space. This results in adjacent memory being overwritten, corrupting critical data structures and causing the device to crash.

The denial of service impact is particularly significant for IoT devices like routers, as they serve as network gateways. A successful exploit would disconnect all devices relying on the affected router for network connectivity.

Root Cause

The root cause of this vulnerability is insufficient input validation in the tgfile_htm function. The firmware code accepts the fn parameter from user requests without verifying that the input length does not exceed the destination buffer's capacity. This is a common programming error in C/C++ code where functions like strcpy() or sprintf() are used without length restrictions, or where buffer sizes are miscalculated.

Attack Vector

An attacker can exploit this vulnerability by sending a specially crafted HTTP request to the D-Link DI-8300's web management interface. The malicious request would include an oversized value for the fn parameter in a request targeting the tgfile_htm function.

The attack requires network access to the device's management interface. If the management interface is exposed to the internet (which is not recommended but often occurs), the attack could be performed remotely. In typical deployments where the management interface is only accessible from the local network, an attacker would need to be on the same network segment or have compromised another device on the network.

The vulnerability is triggered when the oversized fn parameter is processed, causing the buffer overflow and resulting in a denial of service condition that crashes the router.

Detection Methods for CVE-2025-45059

Indicators of Compromise

• Unexpected router reboots or service interruptions on D-Link DI-8300 devices
• Abnormally long HTTP request parameters in web management interface logs
• Network connectivity disruptions coinciding with suspicious traffic to the router's management port
• Crash dump files or error logs indicating memory corruption in firmware processes

Detection Strategies

• Monitor HTTP traffic to D-Link DI-8300 management interfaces for requests containing unusually long fn parameter values
• Implement network-based intrusion detection rules to identify buffer overflow attempts targeting IoT device management interfaces
• Deploy network segmentation to isolate IoT device management traffic for enhanced monitoring visibility
• Configure alerts for repeated router crashes or unexpected device reboots

Monitoring Recommendations

• Enable logging on the D-Link DI-8300 if supported by firmware and regularly review logs for anomalous activity
• Implement network traffic analysis tools to baseline normal traffic patterns and detect deviations
• Monitor for port scanning activity targeting common router management ports (80, 443, 8080)
• Establish automated alerts for D-Link device availability to quickly detect DoS conditions

How to Mitigate CVE-2025-45059

Immediate Actions Required

• Restrict access to the D-Link DI-8300 web management interface to trusted IP addresses only
• Disable remote management access from the WAN interface if not required
• Place the device behind a firewall that can filter malicious requests
• Monitor D-Link security bulletins for firmware updates addressing this vulnerability
• Consider replacing end-of-life devices with currently supported models

Patch Information

At the time of publication, administrators should consult the D-Link Security Bulletin for the latest information on available patches. Check the D-Link Product Information Page for firmware updates specific to the DI-8300 model. Additional technical details about this vulnerability are available in the GitHub IoT Vulnerability Collection.

Workarounds

• Implement access control lists (ACLs) on upstream network devices to restrict management interface access to authorized administrators only
• Use a VPN for remote management rather than exposing the management interface directly
• Deploy a web application firewall (WAF) or intrusion prevention system (IPS) that can inspect and block requests with oversized parameters
• Disable the web management interface entirely if not needed and manage the device through alternative methods if available
• Segment IoT devices onto a dedicated VLAN with strict ingress and egress filtering

# Example: Restrict management access using upstream firewall rules
# Block external access to router management interface
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 443 -j ACCEPT