Description

A security flaw has been discovered in D-Link DI-8400 16.07. This affects the function ddns_asp of the file /ddns.asp of the component DDNS Configuration. Performing a manipulation of the argument serv/user/host/wild/mx/bmx/cust/ip results in stack-based buffer overflow. The attack can be initiated remotely. The exploit has been released to the public and may be used for attacks.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-09-15T06:16:59.970Z",
  "pubdate": "2026-09-15T06:16:59.970Z",
  "executiveSummary": "A critical stack-based buffer overflow vulnerability exists in the D-Link DI-8400 router, specifically within the DDNS configuration handling mechanism. This flaw allows a remote, unauthenticated attacker to inject arbitrary data into the system stack, potentially leading to remote code execution or a complete denial-of-service state.\nThe vulnerability is situated within the 'ddns_asp' function of the '/ddns.asp' file. By manipulating various input parameters such as 'serv', 'user', 'host', 'wild', 'mx', 'bmx', 'cust', or 'ip', an attacker can trigger memory corruption by supplying input that exceeds the allocated buffer size.\nGiven that proof-of-concept exploit code has been released publicly, the risk to unpatched devices is high. Successful exploitation grants an attacker the capability to execute malicious payloads with the privileges of the underlying web service process, which frequently possesses elevated system permissions on embedded networking hardware. Users of the D-Link DI-8400 are advised to restrict device management access to trusted internal networks and monitor for unusual traffic patterns targeting administrative web interfaces.",
  "technicalDetails": "The vulnerability is a classic stack-based buffer overflow located within the 'ddns_asp' function, which is invoked by the '/ddns.asp' script responsible for Dynamic DNS (DDNS) configuration on the D-Link DI-8400 firmware version 16.07.\nThe root cause of the vulnerability lies in the improper handling of user-supplied input strings. When the web server processes an HTTP request targeting '/ddns.asp', the 'ddns_asp' function captures values associated with parameters including 'serv', 'user', 'host', 'wild', 'mx', 'bmx', 'cust', and 'ip'. The function fails to perform adequate bounds checking on these input fields before copying the data into a fixed-length buffer located on the stack.\nExploitation is achieved by providing a malicious, oversized string as an argument to one of the identified parameters. Because the 'ddns_asp' function does not enforce length constraints during the memory copy operation (likely utilizing unsafe functions like 'strcpy' or 'sprintf'), the excess input data overflows the destination buffer. This overflow overwrites adjacent memory, including the function's saved frame pointer and the return address stored on the stack.\nBy carefully crafting the payload, an attacker can overwrite the return address with the address of a chosen instruction sequence—such as a NOP sled leading to shellcode or an address pointing to existing 'gadgets' within the firmware (Return-Oriented Programming, or ROP). When the 'ddns_asp' function completes its execution and attempts to return to its caller, control flow is redirected to the attacker's injected code or chosen execution path.\nThe attack is remotely executable, meaning it does not require physical access to the device. Because the DDNS configuration interface is often accessible via the WAN or LAN web management portal, the network exposure is significant. Successful exploitation results in the compromise of the device's control logic, allowing for persistence, data exfiltration, or complete system takeover. Post-exploitation impact may include the modification of device settings, redirection of traffic, or the incorporation of the device into a botnet, as the process typically runs with sufficient privileges to execute arbitrary system commands."
}