CVE-2025-6616: D-Link DIR-619L Buffer Overflow Vulnerability

CVE-2025-6616 Overview

CVE-2025-6616 is a stack-based buffer overflow vulnerability in the D-Link DIR-619L router running firmware version 2.06B01. The flaw resides in the formSetWAN_Wizard51 function within /goform/formSetWAN_Wizard51, where the curTime argument is processed without proper bounds checking. Attackers can trigger the overflow remotely over the network. The vulnerability has been publicly disclosed and the proof-of-concept is available on GitHub. D-Link has confirmed that the DIR-619L is end-of-life and will not receive a patch, leaving deployed devices permanently exposed.

Critical Impact
Remote attackers can exploit the curTime parameter to corrupt the stack and potentially gain arbitrary code execution on unpatched DIR-619L routers, with no vendor fix forthcoming.

Affected Products

D-Link DIR-619L hardware revision (end-of-life)
D-Link DIR-619L firmware version 2.06B01
Any deployment exposing the /goform/formSetWAN_Wizard51 endpoint

Discovery Timeline

2025-06-25 - CVE-2025-6616 published to NVD
2025-07-14 - Last updated in NVD database

Technical Details for CVE-2025-6616

Vulnerability Analysis

The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and manifests as a stack-based buffer overflow. The formSetWAN_Wizard51 handler processes WAN configuration requests submitted through the router's web interface. When an attacker supplies an oversized value to the curTime parameter, the function copies user-controlled data onto a fixed-size stack buffer without validating the input length.

The overflow overwrites adjacent stack memory, including saved return addresses and frame pointers. Successful exploitation can redirect execution flow to attacker-controlled code, leading to arbitrary code execution under the privileges of the embedded web server process. On D-Link consumer routers, this typically equates to root-level command execution.

Root Cause

The root cause is missing length validation on the curTime HTTP parameter before it is copied into a stack-allocated buffer inside formSetWAN_Wizard51. The firmware relies on unsafe string handling routines without enforcing maximum input size, a recurring weakness in legacy MIPS-based D-Link firmware images.

Attack Vector

An attacker reaches the vulnerable endpoint by submitting a crafted HTTP request to /goform/formSetWAN_Wizard51 containing an oversized curTime value. The attack requires network reachability to the router's management interface and low-privilege authentication. Devices exposing the web UI to the WAN side are reachable directly from the internet. Public proof-of-concept material has been documented in the GitHub vulnerability writeup and the corresponding VulDB entry #313834.

No verified exploit code is reproduced here. Refer to the GitHub PoC reference for technical details.

Detection Methods for CVE-2025-6616

Indicators of Compromise

HTTP POST requests to /goform/formSetWAN_Wizard51 containing unusually long curTime parameter values
Unexpected reboots, crash logs, or watchdog resets on DIR-619L devices following inbound web requests
New outbound connections from the router to unfamiliar IP addresses or non-standard ports
DNS configuration changes or modified WAN settings without administrator action

Detection Strategies

Inspect router web traffic at network choke points for requests targeting /goform/formSetWAN_Wizard51 with curTime payloads exceeding expected length
Deploy IDS/IPS signatures that match oversized parameter values in D-Link formSet* endpoints
Baseline DIR-619L firmware behavior and alert on deviations such as unexpected process spawning or configuration drift
Correlate router syslog entries with perimeter firewall logs to identify exploitation attempts

Monitoring Recommendations

Forward router syslog data to a centralized logging platform for retention and analysis
Monitor for HTTP requests to /goform/* endpoints originating from untrusted network segments
Track outbound traffic volumes from router management interfaces, which should remain near zero
Alert on administrative configuration changes performed outside approved maintenance windows

How to Mitigate CVE-2025-6616

Immediate Actions Required

Replace the D-Link DIR-619L with a supported router model, as the device is end-of-life and will not receive a security patch
Disable remote management on the WAN interface to prevent internet-based exploitation of the web UI
Restrict LAN-side access to the router's administrative interface to a dedicated management VLAN or trusted hosts
Rotate router administrator credentials and any pre-shared keys that may have been exposed

Patch Information

No patch is available. D-Link has confirmed the DIR-619L is no longer supported by the maintainer. Vendor advisory information is available on the D-Link Official Website. Organizations must decommission affected hardware to fully remediate the vulnerability.

Workarounds

Place affected routers behind a separately managed firewall and block inbound traffic to the management interface
Segment the router onto an isolated network and disable any port-forwarding rules that expose /goform/* paths
Use a VPN to reach the management interface rather than exposing it over HTTP
Monitor for the device's eventual replacement and treat the router as untrusted until removed from service

bash

# Example firewall rule to block external access to the router web UI
# Replace <ROUTER_IP> with the affected device's address
iptables -A FORWARD -p tcp -d <ROUTER_IP> --dport 80 -i <WAN_IFACE> -j DROP
iptables -A FORWARD -p tcp -d <ROUTER_IP> --dport 443 -i <WAN_IFACE> -j DROP