CVE-2025-4451: D-Link DIR-619L Buffer Overflow Vulnerability

CVE-2025-4451 Overview

A critical buffer overflow vulnerability has been identified in the D-Link DIR-619L wireless router firmware version 2.04B04. The vulnerability exists in the formSetWAN_Wizard52 function, where improper handling of the curTime argument allows for a classic buffer overflow condition. This flaw can be exploited remotely by authenticated attackers to potentially execute arbitrary code or cause a denial of service on affected devices.

Critical Impact

This vulnerability affects an end-of-life product that no longer receives security updates from D-Link, leaving exposed devices permanently vulnerable to remote exploitation.

Affected Products

• D-Link DIR-619L Firmware version 2.04B04
• D-Link DIR-619L Hardware (all revisions running affected firmware)

Discovery Timeline

• 2025-05-09 - CVE-2025-4451 published to NVD
• 2025-05-13 - Last updated in NVD database

Technical Details for CVE-2025-4451

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-120 (Buffer Copy without Checking Size of Input). The formSetWAN_Wizard52 function within the router's web management interface fails to properly validate the length of the curTime parameter before copying it into a fixed-size buffer. When an attacker supplies an oversized value for this parameter, it overwrites adjacent memory regions, potentially corrupting function return addresses, control flow data, or other critical memory structures.

The vulnerability is particularly concerning because the D-Link DIR-619L has reached end-of-life status. D-Link has confirmed they were contacted about this vulnerability but will not be releasing a patch since the product is no longer supported.

Root Cause

The root cause stems from unsafe memory handling practices in the router's firmware. The formSetWAN_Wizard52 function uses a buffer copy operation without implementing proper bounds checking on the curTime input parameter. This is a classic buffer overflow scenario where user-controlled input is written to a stack or heap buffer without validating that the input length does not exceed the allocated buffer size.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An attacker with low-privilege authentication to the device can submit a malicious HTTP request containing an oversized curTime parameter value to the WAN wizard configuration endpoint. The vulnerable formSetWAN_Wizard52 function processes this request, triggering the buffer overflow condition.

The vulnerability requires:

• Network access to the router's management interface
• Low-level authentication (user credentials)
• No user interaction required

Technical details and proof-of-concept information are available in the GitHub PoC Repository.

Detection Methods for CVE-2025-4451

Indicators of Compromise

• Unexpected reboots or crashes of the D-Link DIR-619L router
• Unusual HTTP POST requests to the WAN wizard configuration endpoints with abnormally large parameter values
• Anomalous traffic patterns originating from the router's management interface
• Signs of unauthorized firmware modification or configuration changes

Detection Strategies

• Monitor network traffic for HTTP requests to D-Link DIR-619L management interfaces containing the curTime parameter with values exceeding normal lengths
• Implement intrusion detection rules to identify buffer overflow exploitation patterns targeting embedded device web interfaces
• Use network segmentation monitoring to detect unexpected outbound connections from router management interfaces
• Deploy SentinelOne Singularity to detect and alert on exploitation attempts targeting network infrastructure devices

Monitoring Recommendations

• Audit all D-Link DIR-619L devices on the network and inventory their firmware versions
• Implement network-level logging for all traffic to and from router management interfaces
• Configure alerts for authentication attempts against the router's web interface from unusual source addresses
• Review router logs periodically for evidence of exploitation attempts or unauthorized access

How to Mitigate CVE-2025-4451

Immediate Actions Required

• Immediately disable remote management access to the DIR-619L from untrusted networks
• Restrict access to the router's web management interface to trusted internal IP addresses only
• Place affected routers behind an additional firewall layer that blocks external access to management ports
• Begin planning for device replacement as this product is end-of-life and will not receive security patches

Patch Information

No patch is available for this vulnerability. D-Link has confirmed that the DIR-619L router is an end-of-life product that no longer receives security updates or maintenance. The vendor was contacted during the responsible disclosure process but will not be releasing a fix.

Organizations are strongly advised to replace affected devices with currently supported hardware that receives regular security updates.

Workarounds

• Disable the router's web-based management interface entirely if administrative access is not required
• Implement strict network access control lists (ACLs) to limit management interface access to specific administrator workstations
• Configure firewall rules to block all inbound connections to the router's management ports (typically HTTP port 80 or HTTPS port 443)
• Consider replacing the device with a supported router model that receives security updates

# Example: Block external access to router management (on upstream firewall)
# Replace 192.168.1.1 with your DIR-619L IP address
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT