CVE-2026-7247: D-Link DI-8100 Buffer Overflow Vulnerability

CVE-2026-7247 Overview

A buffer overflow vulnerability has been discovered in D-Link DI-8100 router firmware version 16.07.26A1. The vulnerability exists in the file_exten_asp function within the file_exten.asp component, which handles file extension operations. Improper validation of the Name argument allows an attacker to trigger a buffer overflow condition, potentially leading to remote code execution or denial of service on the affected device.

Critical Impact

This network-exploitable buffer overflow in the D-Link DI-8100 router allows authenticated attackers to execute arbitrary code or cause system crashes by sending specially crafted requests to the File Extension Handler component.

Affected Products

• D-Link DI-8100 Router
• D-Link DI-8100 Firmware version 16.07.26A1
• D-Link DI-8100 devices with vulnerable File Extension Handler component

Discovery Timeline

• 2026-04-28 - CVE-2026-7247 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7247

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the file_exten_asp function responsible for processing file extension configurations on the D-Link DI-8100 router. When the Name parameter is processed, the function fails to properly validate the length of the input data before copying it into a fixed-size memory buffer.

The exploit has been publicly disclosed and proof-of-concept details are available, increasing the risk of active exploitation against unpatched devices. While exploitation requires authenticated access (high privileges), the network-accessible nature of the vulnerability means that attackers with valid credentials can exploit this remotely without any user interaction.

Root Cause

The root cause stems from insufficient bounds checking in the file_exten_asp function within file_exten.asp. When processing the Name argument, the function copies user-supplied data into a stack-based buffer without verifying that the input length does not exceed the allocated buffer size. This classic buffer overflow condition allows an attacker to overwrite adjacent memory regions, potentially corrupting function return addresses or other critical data structures.

Attack Vector

The attack can be executed remotely over the network by an authenticated attacker with administrative privileges on the D-Link DI-8100 device. The attacker crafts a malicious HTTP request to the file_exten.asp endpoint with an oversized Name parameter value. When the vulnerable function processes this request, the excessive data overflows the allocated buffer, leading to memory corruption.

The vulnerability manifests in the file extension handler component when processing malformed input. Attackers can target the file_exten.asp endpoint with specially crafted Name parameter values that exceed expected buffer boundaries. Technical details and analysis of the overflow condition can be found in the GitHub Overflow Report.

Detection Methods for CVE-2026-7247

Indicators of Compromise

• Unexpected router reboots or service crashes, particularly affecting web management interfaces
• Anomalous HTTP POST requests to file_exten.asp with unusually long Name parameter values
• Memory corruption errors or segmentation faults in router logs
• Unauthorized configuration changes or new user accounts on the device

Detection Strategies

• Monitor network traffic for HTTP requests targeting file_exten.asp with abnormally large parameter values
• Implement intrusion detection signatures to flag requests with Name parameters exceeding normal operational lengths
• Review web server access logs for repeated failed requests or suspicious patterns targeting the File Extension Handler
• Deploy network-based anomaly detection to identify buffer overflow attack patterns against embedded devices

Monitoring Recommendations

• Enable comprehensive logging on D-Link DI-8100 devices if available
• Implement network segmentation to isolate IoT and network devices from general network traffic
• Monitor for authentication attempts followed by requests to vulnerable endpoints
• Consider deploying a web application firewall (WAF) in front of router management interfaces if externally accessible

How to Mitigate CVE-2026-7247

Immediate Actions Required

• Restrict access to the D-Link DI-8100 web management interface to trusted internal networks only
• Implement strong, unique administrative credentials and enable multi-factor authentication if supported
• Consider temporarily disabling the web management interface if not required for operations
• Place the device behind a firewall with strict access control rules limiting management access

Patch Information

At the time of publication, no official patch information has been released by D-Link for this vulnerability. Organizations should monitor the D-Link Security Resource page for firmware updates addressing CVE-2026-7247. Additional technical details can be found at VulDB #359856.

Workarounds

• Disable remote management access to the D-Link DI-8100 device and allow only local console access
• Implement network ACLs to restrict which IP addresses can reach the device management interface
• Deploy an application-layer firewall to filter and validate requests to the file_exten.asp endpoint
• Consider replacing the affected device with an alternative solution if a patch is not forthcoming

# Configuration example - Restrict management interface access via iptables on upstream firewall
# Allow management access only from trusted admin subnet
iptables -A FORWARD -d <DI-8100_IP> -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A FORWARD -d <DI-8100_IP> -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
# Block all other management access
iptables -A FORWARD -d <DI-8100_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <DI-8100_IP> -p tcp --dport 443 -j DROP