CVE-2025-4450: D-Link DIR-619L Buffer Overflow Vulnerability

CVE-2025-4450 Overview

CVE-2025-4450 is a buffer overflow vulnerability affecting the D-Link DIR-619L router running firmware version 2.04B04. The flaw resides in the formSetEasy_Wizard function, where improper handling of the curTime argument allows attackers to overflow a fixed-size buffer. Exploitation can be performed remotely over the network and requires only low-level privileges on the device.

The affected device is end-of-life and no longer supported by D-Link, meaning no official patch will be released. The vendor was contacted before public disclosure but does not maintain this product line.

Critical Impact
Remote attackers with low-privilege access can trigger memory corruption in the DIR-619L web management interface, potentially leading to arbitrary code execution and full compromise of the router.

Affected Products

D-Link DIR-619L router (hardware revision affected by firmware 2.04B04)
D-Link DIR-619L firmware version 2.04B04
All earlier firmware revisions on the end-of-life DIR-619L platform

Discovery Timeline

2025-05-09 - CVE-2025-4450 published to NVD
2025-05-13 - Last updated in NVD database

Technical Details for CVE-2025-4450

Vulnerability Analysis

The vulnerability is a classic stack or heap buffer overflow [CWE-119, CWE-120] in the router's web administration interface. The formSetEasy_Wizard handler processes the curTime parameter without enforcing length checks before copying the input into a fixed-size buffer. Attackers can submit oversized values to corrupt adjacent memory regions on the device.

Because the DIR-619L is no longer supported, the firmware lacks modern memory protections found in current router platforms. Successful exploitation can overwrite control structures and redirect execution flow on the MIPS-based embedded system. The result ranges from denial of service to remote code execution under the privileges of the web server process, which typically runs as root on consumer routers.

Root Cause

The root cause is missing input validation on the curTime argument inside formSetEasy_Wizard. The function trusts client-supplied data and performs an unsafe copy operation, likely using strcpy, sprintf, or memcpy without bounds enforcement. This pattern is common in legacy D-Link firmware compiled from the SDK base used across the DIR-6xx series.

Attack Vector

An authenticated attacker on the same network as the router can send a crafted HTTP request to the Easy Setup Wizard endpoint with an oversized curTime value. If the management interface is exposed to the WAN, the attack can be launched from the internet. Exploitation does not require user interaction. Technical proof-of-concept details are documented in the GitHub PoC Repository and tracked as VulDB #308064.

Detection Methods for CVE-2025-4450

Indicators of Compromise

HTTP POST requests to the DIR-619L web interface targeting formSetEasy_Wizard with abnormally long curTime parameter values.
Unexpected reboots, watchdog resets, or crashes of the httpd process on the router.
Outbound connections from the router to unknown hosts, indicating potential post-exploitation implant activity.
DNS configuration changes or new administrative accounts appearing on the device.

Detection Strategies

Inspect network traffic destined for the router management interface and flag requests where curTime exceeds expected length boundaries.
Monitor for HTTP requests to the Easy Setup Wizard endpoint originating from untrusted network segments or the WAN side.
Correlate router availability dips with inbound HTTP traffic patterns to identify exploitation attempts that crash the device.

Monitoring Recommendations

Place legacy D-Link devices behind a network segment monitored by an intrusion detection system with custom signatures for formSetEasy_Wizard abuse.
Log all administrative access attempts to the router and alert on requests containing oversized query parameters.
Track DNS resolution patterns from clients behind the router to identify hijacked resolver settings.

How to Mitigate CVE-2025-4450

Immediate Actions Required

Replace the DIR-619L with a currently supported router model, since the product is end-of-life and will not receive a patch.
Disable remote (WAN-side) management on the device immediately to limit the attack surface to local network attackers.
Restrict access to the LAN-side web interface using firewall rules or VLAN segmentation until the device can be retired.
Change the administrative password and audit configured DNS servers, port forwards, and admin accounts for unauthorized changes.

Patch Information

No patch is available. D-Link has confirmed that the DIR-619L is no longer supported and will not receive security updates for this issue. Decommissioning the device is the only complete remediation. Reference advisories are available at VulDB CTI ID #308064 and the D-Link Official Website for end-of-life guidance.

Workarounds

Block inbound access to TCP port 80 and 443 on the WAN interface of the router.
Place the router behind an upstream firewall that filters HTTP traffic to the management interface from untrusted networks.
If the device must remain in service temporarily, isolate it on a dedicated management VLAN reachable only from a hardened jump host.

bash

# Example: block external access to DIR-619L management interface from an upstream Linux gateway
iptables -A FORWARD -d <router_lan_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_lan_ip> -p tcp --dport 443 -j DROP
iptables -A FORWARD -i wan0 -d <router_lan_ip> -j DROP