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This vulnerability resides in the D-Link DIR-513 router’s web server (Boa). The `formLogin` handler, accessible via the `/goform/formLogin` endpoint, utilizes the `sprintf` function to copy the `curTime` parameter from a POST request into a fixed-size stack buffer without checking its length. By supplying an excessively long `curTime` value, an attacker can overflow this buffer, overwriting adjacent memory on the stack including the return address. This allows for remote code execution with the device’s root privileges, leading to full system compromise. The device is end-of-life and will not receive a patch .
Platform: D-Link DIR-513
Version: v1.10
Vulnerability : Stack Buffer Overflow
Severity: Critical (CVSS 9.8)
date: 03/04/2026
Prediction: No Patch (EOL)
What Undercode Say:
Analytics:
The vulnerability is caused by the unsafe use of `sprintf` in the Boa webserver’s `formLogin` function. Attackers can exploit this remotely without authentication by sending a crafted HTTP POST request.
Example of discovering the vulnerable endpoint with nmap
nmap -p 80 --script http-enum <target-ip>
Simulating the overflow with a long string using curl
curl -X POST http://<target-ip>/goform/formLogin \
-d "curTime=$(python3 -c 'print("A" 5000)')"
How Exploit:
Exploitation involves sending a POST request to `/goform/formLogin` with a `curTime` parameter exceeding the buffer capacity. Public Proof-of-Concept (PoC) code exists, demonstrating control over the instruction pointer to redirect execution to attacker-controlled shellcode .
Simple PoC structure (conceptual)
import requests
5000 bytes of 'A' to trigger the overflow
payload = 'A' 5000
The shellcode would be placed strategically within the payload
to gain a reverse shell or execute arbitrary commands.
requests.post('http://<target_ip>/goform/formLogin', data={'curTime': payload})
Protection from this CVE:
Since the device is End-of-Life (EOL) and no patch is available, the only effective protection is to replace the device. Immediate mitigations include isolating the router on a separate network segment and disabling remote management features to limit exposure .
Iptables rule to drop incoming traffic to the vulnerable endpoint (Example) iptables -A INPUT -p tcp --dport 80 -m string --string "/goform/formLogin" --algo bm -j DROP
Impact:
Successful exploitation results in complete device compromise, allowing attackers to monitor network traffic, launch attacks on internal systems, and use the router as a persistent foothold within the network .
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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D-Link DIR-513, Stack Buffer Overflow, CVE-2025-70222 (Critical)