CVE-2025-4355: D-Link DAP-1520 Buffer Overflow Vulnerability

CVE-2025-4355 Overview

A critical heap-based buffer overflow vulnerability has been identified in the Tenda DAP-1520 wireless range extender firmware version 1.10B04_BETA02. This vulnerability affects the set_ws_action function within the /dws/api/ endpoint and can be exploited remotely by authenticated attackers to achieve arbitrary code execution, potentially leading to complete device compromise.

Critical Impact

Remote attackers with low privileges can exploit this heap-based buffer overflow to execute arbitrary code on vulnerable Tenda DAP-1520 devices, potentially gaining full control over the network device and using it as a pivot point for further attacks.

Affected Products

• Tenda DAP-1520 Firmware version 1.10B04_BETA02
• Tenda DAP-1520 Hardware revision A1
• D-Link DAP-1520 (related firmware)

Discovery Timeline

• May 6, 2025 - CVE-2025-4355 published to NVD
• May 13, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4355

Vulnerability Analysis

This vulnerability is a heap-based buffer overflow (CWE-787, CWE-119) that occurs in the set_ws_action function of the Tenda DAP-1520 firmware. The function, accessible via the /dws/api/ endpoint, fails to properly validate the length of user-supplied input before copying it to a fixed-size heap buffer. This allows an attacker to overflow the buffer boundaries and corrupt adjacent heap memory structures.

The vulnerability is particularly dangerous because it can be triggered remotely over the network. While exploitation requires low-level privileges (authenticated access), the attack complexity is low and requires no user interaction. Successful exploitation could result in complete compromise of the device's confidentiality, integrity, and availability.

Root Cause

The root cause of this vulnerability stems from improper buffer size validation in the set_ws_action function. When processing API requests to the /dws/api/ endpoint, the function allocates a heap buffer of a fixed size but does not adequately verify that incoming data fits within this allocation. The lack of boundary checking before memory copy operations allows attacker-controlled data to overflow the allocated buffer space.

This is a classic memory safety issue common in embedded device firmware written in C/C++ where manual memory management is required but not properly implemented.

Attack Vector

The attack is network-based and targets the /dws/api/ endpoint on the device's web management interface. An attacker with network access to the vulnerable device and valid credentials (low privilege requirement) can craft a malicious HTTP request containing oversized data that triggers the buffer overflow in the set_ws_action function.

The exploitation process involves:

1. Establishing network connectivity to the target Tenda DAP-1520 device
2. Authenticating to the device's web interface with minimal privileges
3. Sending a crafted request to /dws/api/ with malicious payload targeting the set_ws_action function
4. Overflowing the heap buffer to corrupt memory and potentially redirect execution flow

Technical details of the vulnerability have been documented publicly. For more information, see the GitHub IoT Documentation and the VulDB Vulnerability Report.

Detection Methods for CVE-2025-4355

Indicators of Compromise

• Unusual HTTP requests to /dws/api/ endpoint with abnormally large payloads or malformed parameters
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Anomalous outbound network connections from the DAP-1520 device suggesting command-and-control communication
• Log entries showing repeated authentication followed by API calls to the affected endpoint

Detection Strategies

• Implement network-level monitoring to identify HTTP requests with oversized payloads targeting the /dws/api/ endpoint
• Deploy intrusion detection signatures to flag requests containing buffer overflow attack patterns against Tenda devices
• Monitor device logs for crash events or unexpected service restarts that may indicate exploitation attempts
• Conduct regular firmware version audits to identify devices running vulnerable firmware version 1.10B04_BETA02

Monitoring Recommendations

• Configure alerts for unusual traffic patterns to IoT devices on the network, particularly targeting web management interfaces
• Implement network segmentation to isolate IoT devices like the DAP-1520 from critical network assets
• Enable logging on network security appliances to capture traffic destined for known vulnerable endpoints
• Establish baseline behavior for the device and alert on deviations that may indicate compromise

How to Mitigate CVE-2025-4355

Immediate Actions Required

• Isolate vulnerable Tenda DAP-1520 devices from critical network segments immediately
• Restrict network access to the device's web management interface using firewall rules or access control lists
• Disable remote management features if not required for operation
• Review device logs for signs of prior exploitation attempts

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for security updates and firmware releases. Given the public disclosure of this vulnerability, applying patches immediately upon availability is critical.

For the latest vulnerability information, consult the VulDB entry.

Workarounds

• Implement strict network access controls to limit which hosts can communicate with the vulnerable device
• Place the DAP-1520 behind a firewall with rules blocking external access to the web management interface
• Consider replacing the vulnerable device with a product that receives active security support if no patch becomes available
• Use network-level intrusion prevention systems to block known attack patterns targeting this vulnerability

# Example: Network isolation using iptables
# Block external access to the device's web management port
iptables -A INPUT -p tcp --dport 80 -d <DAP-1520_IP> -j DROP
iptables -A INPUT -p tcp --dport 443 -d <DAP-1520_IP> -j DROP

# Allow only trusted management hosts
iptables -A INPUT -p tcp --dport 80 -s <TRUSTED_MGMT_IP> -d <DAP-1520_IP> -j ACCEPT