CVE-2025-70239 Overview
A stack buffer overflow vulnerability exists in the D-Link DIR-513 router firmware version 1.10. The vulnerability is triggered via the curTime parameter sent to the goform/formSetWAN_Wizard55 endpoint. This flaw allows unauthenticated remote attackers to potentially execute arbitrary code or cause a denial of service condition on affected devices.
Critical Impact
This stack buffer overflow vulnerability can be exploited remotely without authentication, potentially allowing attackers to gain complete control of affected D-Link DIR-513 routers, compromise network security, and pivot to other devices on the network.
Affected Products
- D-Link DIR-513 Firmware version 1.10
- D-Link DIR-513 Hardware (all revisions running vulnerable firmware)
Discovery Timeline
- 2026-03-03 - CVE-2025-70239 published to NVD
- 2026-03-04 - Last updated in NVD database
Technical Details for CVE-2025-70239
Vulnerability Analysis
This vulnerability is classified as CWE-787 (Out-of-Bounds Write), manifesting as a stack buffer overflow in the D-Link DIR-513 router's web management interface. The vulnerable endpoint goform/formSetWAN_Wizard55 fails to properly validate the length of user-supplied input in the curTime parameter before copying it to a fixed-size stack buffer.
When an attacker sends an HTTP request with an excessively long curTime parameter value, the data overflows the allocated stack buffer, potentially overwriting adjacent memory including the return address. This can lead to arbitrary code execution in the context of the web server process, which typically runs with elevated privileges on embedded devices.
The network-accessible nature of this vulnerability means it can be exploited remotely without any authentication or user interaction, making it particularly dangerous for internet-exposed routers.
Root Cause
The root cause is improper input validation in the form handler for the WAN configuration wizard. The firmware fails to implement proper bounds checking when processing the curTime parameter, allowing attackers to overflow a stack-allocated buffer. This is a common vulnerability pattern in embedded device firmware where memory-safe string handling functions are not consistently used.
Attack Vector
The attack vector is network-based, targeting the HTTP-based web management interface of the D-Link DIR-513 router. An attacker can craft a malicious HTTP POST request to the goform/formSetWAN_Wizard55 endpoint with an oversized curTime parameter. Since this endpoint is accessible without authentication, the vulnerability can be exploited by any attacker who can reach the router's management interface, whether on the local network or, in misconfigured deployments, from the internet.
The exploitation flow involves sending a specially crafted HTTP request that triggers the buffer overflow, potentially allowing the attacker to overwrite control data on the stack and redirect execution to attacker-controlled code.
Detection Methods for CVE-2025-70239
Indicators of Compromise
- Unusual HTTP POST requests to goform/formSetWAN_Wizard55 with abnormally long parameter values
- Unexpected router reboots or crashes that may indicate exploitation attempts
- Modified router configurations or unauthorized administrative access
- Suspicious outbound network connections from the router to unknown external hosts
Detection Strategies
- Monitor network traffic for HTTP requests containing oversized curTime parameters targeting D-Link management endpoints
- Implement intrusion detection rules to alert on suspicious traffic patterns to goform/ endpoints
- Review router logs for repeated access attempts to the WAN wizard configuration endpoint
- Deploy network-based anomaly detection to identify unusual behavior from router devices
Monitoring Recommendations
- Enable logging on network firewalls to capture traffic destined for router management interfaces
- Configure SIEM alerts for multiple failed or unusual requests to D-Link device management URLs
- Regularly audit router configuration for unauthorized changes
- Monitor for unexpected DNS changes or traffic redirection that could indicate router compromise
How to Mitigate CVE-2025-70239
Immediate Actions Required
- Restrict access to the router's web management interface to trusted internal networks only
- Disable remote management features if not strictly required
- Implement firewall rules to block external access to the router's administrative ports
- Consider network segmentation to isolate vulnerable devices from critical assets
Patch Information
D-Link has been notified of this vulnerability. Users should monitor the D-Link Security Bulletin for firmware updates addressing this issue. Given the age of the DIR-513 model, users should verify whether the device is still within its support lifecycle and eligible for security updates.
Additional technical details about this vulnerability can be found in the GitHub CVE Report.
Workarounds
- Disable the web management interface entirely if administration can be performed through other means
- Place the router behind a separate firewall that can filter malicious requests
- Use VPN to access the management interface instead of exposing it directly
- Consider replacing end-of-life devices with currently supported models that receive security updates
# Example: Restrict management interface access via iptables on upstream device
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP
# Allow only from trusted management subnet
iptables -I FORWARD -s 192.168.1.0/24 -d <router_ip> -p tcp --dport 80 -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
