CVE-2025-70236: D-Link DIR-513 Buffer Overflow Flaw

CVE-2025-70236 Overview

A stack buffer overflow vulnerability has been discovered in the D-Link DIR-513 router firmware version 1.10. The vulnerability exists in the goform/formSetDomainFilter endpoint, where the curTime parameter is improperly handled, allowing attackers to overflow a stack-based buffer. This firmware vulnerability affects consumer-grade networking equipment and can be exploited remotely without authentication, potentially allowing complete device compromise.

Critical Impact

Unauthenticated remote attackers can exploit this stack buffer overflow to execute arbitrary code on the affected D-Link DIR-513 router, potentially gaining full control of the device and using it as a pivot point for further network attacks.

Affected Products

• D-Link DIR-513 Firmware version 1.10
• D-Link DIR-513 Hardware

Discovery Timeline

• 2026-03-03 - CVE-2025-70236 published to NVD
• 2026-03-04 - Last updated in NVD database

Technical Details for CVE-2025-70236

Vulnerability Analysis

This vulnerability is classified under CWE-787 (Out-of-bounds Write) and CWE-121 (Stack-based Buffer Overflow). The flaw resides in the web management interface of the D-Link DIR-513 router, specifically within the domain filter configuration functionality. When processing HTTP requests to goform/formSetDomainFilter, the firmware fails to properly validate the length of the curTime parameter before copying it to a fixed-size stack buffer.

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction. Successful exploitation could allow an attacker to overwrite critical stack values including the return address, enabling arbitrary code execution with the privileges of the web server process running on the embedded device.

Root Cause

The root cause of this vulnerability is improper input validation in the web form processing code. The curTime parameter is accepted from user-supplied HTTP POST data and copied into a stack-allocated buffer without adequate bounds checking. This classic stack buffer overflow pattern occurs when the firmware uses unsafe string handling functions or fails to verify that input data fits within the allocated buffer space before performing the copy operation.

Attack Vector

The attack is network-based and targets the router's web management interface. An attacker can craft a malicious HTTP POST request to the goform/formSetDomainFilter endpoint containing an oversized curTime parameter value. The attack does not require authentication, making any exposed D-Link DIR-513 router with firmware version 1.10 potentially vulnerable.

The attacker sends a specially crafted HTTP request containing an excessively long string in the curTime parameter. When the vulnerable function processes this request, the oversized input overwrites adjacent stack memory, allowing the attacker to control execution flow and potentially execute arbitrary shellcode on the device.

For technical details and proof-of-concept information, refer to the GitHub CVE Report.

Detection Methods for CVE-2025-70236

Indicators of Compromise

• Abnormally large HTTP POST requests targeting /goform/formSetDomainFilter endpoint
• Unexpected outbound connections from the router to unknown IP addresses
• Router configuration changes or unexpected reboots without administrator action
• Network traffic anomalies indicating the router may be participating in botnet activity

Detection Strategies

• Monitor HTTP traffic to router management interfaces for POST requests to goform/formSetDomainFilter with unusually large parameter values
• Implement network intrusion detection rules to identify buffer overflow attempt patterns targeting D-Link devices
• Review router access logs for requests from unauthorized IP addresses to administrative endpoints
• Deploy network-based detection signatures for known D-Link exploitation patterns

Monitoring Recommendations

• Isolate router management interfaces from untrusted networks and monitor access attempts
• Enable logging on network firewalls for traffic destined to router management ports
• Implement anomaly detection for unusual traffic patterns originating from or destined to D-Link devices
• Regularly audit firmware versions across all network infrastructure devices

How to Mitigate CVE-2025-70236

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required for operations
• Place the D-Link DIR-513 behind a firewall that blocks external access to management ports
• Consider replacing end-of-life or unsupported D-Link devices with currently supported alternatives

Patch Information

Consult the D-Link Security Bulletin for official patch availability and firmware updates. For product-specific information, visit the D-Link Product Information page. If no patch is available for this end-of-life product, consider device replacement as the most effective mitigation strategy.

Workarounds

• Disable the web management interface entirely if possible and manage via console only
• Implement network segmentation to isolate the vulnerable router from critical network segments
• Configure firewall rules to allow management access only from specific administrator IP addresses
• Enable MAC address filtering as an additional layer of access control to the management interface

# Example: Firewall rule to restrict management access (on upstream firewall)
# Block external access to router management interface
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 management only from trusted admin workstation
iptables -I FORWARD -s <ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT