CVE-2025-5228: Dlink Di-8100 Buffer Overflow Vulnerability

CVE-2025-5228 Overview

CVE-2025-5228 is a stack-based buffer overflow vulnerability in the D-Link DI-8100 router firmware up to version 20250523. The flaw resides in the httpd_get_parm function within /login.cgi, part of the jhttpd component. Attackers can trigger the overflow by manipulating the notify argument, leading to memory corruption on the stack.

The vulnerability is exploitable from the adjacent network and does not require authentication or user interaction. The exploit has been disclosed publicly, increasing the risk of opportunistic attacks against exposed devices. The issue is classified under CWE-119 for improper restriction of operations within memory buffer bounds.

Critical Impact
Adjacent network attackers can corrupt stack memory in jhttpd and potentially execute arbitrary code on affected D-Link DI-8100 routers without authentication.

Affected Products

D-Link DI-8100 router hardware
D-Link DI-8100 firmware versions up to and including 20250523
Deployments exposing the jhttpd web management interface on local networks

Discovery Timeline

2025-05-27 - CVE-2025-5228 published to the National Vulnerability Database (NVD)
2025-07-15 - Last updated in NVD database

Technical Details for CVE-2025-5228

Vulnerability Analysis

The vulnerability exists in the httpd_get_parm function that parses HTTP parameters in the jhttpd web server. When processing the notify parameter submitted to /login.cgi, the function copies attacker-controlled data into a fixed-size stack buffer without validating input length. This allows adversaries to overflow the buffer and overwrite adjacent stack memory.

Stack-based buffer overflows on embedded MIPS or ARM router platforms typically permit attackers to overwrite the saved return address. With reliable control of the instruction pointer, an attacker can redirect execution to attacker-supplied shellcode or use return-oriented programming (ROP) gadgets present in the firmware. The result is arbitrary code execution under the privileges of the jhttpd process, which on consumer routers commonly runs as root.

The attack requires adjacent network access, meaning the adversary must be on the same local network segment as the target router. Wireless networks, guest networks, and compromised LAN-connected devices all qualify as viable launch points.

Root Cause

The root cause is missing bounds checking in httpd_get_parm when handling the notify HTTP parameter. The function trusts the length of user-supplied input and writes it into a stack-allocated buffer of fixed size. This is a classic violation of safe string handling practices and corresponds to CWE-119.

Attack Vector

An attacker on the adjacent network sends a crafted HTTP request to /login.cgi on the router's management interface. The request contains an oversized value in the notify parameter. When jhttpd invokes httpd_get_parm to retrieve the parameter, the oversized data overflows the destination stack buffer and corrupts control flow data, including the saved return address.

No authentication is required to reach the vulnerable endpoint. The publicly disclosed proof-of-concept details are referenced in the GitHub binary vulnerability report and VulDB entry #310326.

Detection Methods for CVE-2025-5228

Indicators of Compromise

HTTP POST or GET requests to /login.cgi containing abnormally long values in the notify parameter
Unexpected reboots or crashes of the jhttpd process on D-Link DI-8100 devices
Outbound connections from the router to unknown external hosts following management interface access
New or modified configuration entries on the router that were not initiated by an administrator

Detection Strategies

Inspect LAN-side HTTP traffic destined for router management interfaces for oversized parameter values targeting /login.cgi
Deploy network intrusion detection signatures that flag HTTP requests where the notify parameter exceeds expected length boundaries
Correlate router process crash logs with preceding HTTP requests to identify exploitation attempts

Monitoring Recommendations

Forward router syslog data, including web server and authentication logs, to a centralized SIEM for analysis
Monitor for repeated failed connections or malformed HTTP requests targeting the management interface
Track firmware version inventory across deployed D-Link devices to identify unpatched units

How to Mitigate CVE-2025-5228

Immediate Actions Required

Restrict access to the router web management interface to trusted administrative hosts using firewall rules or access control lists
Disable the web management interface on untrusted network segments, including guest Wi-Fi networks
Segment IoT and management networks from general-purpose user networks to limit adjacent network exposure
Audit existing D-Link DI-8100 deployments and replace devices that no longer receive vendor security updates

Patch Information

At the time of publication, no vendor patch is referenced in the available advisory data. Check the D-Link official website and regional D-Link support portals for firmware updates addressing CVE-2025-5228. Apply any updated firmware immediately upon release and verify the running version matches the patched release.

Workarounds

Block external and untrusted internal access to TCP ports serving the jhttpd management interface
Place affected routers behind an additional network firewall that filters HTTP traffic to the management URL paths
Replace the affected DI-8100 device with a currently supported model if no firmware fix is available

bash

# Example iptables rule to restrict management interface access to a trusted admin host
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.10 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP