A vulnerability was determined in Tenda F453 1.0.0.3. Affected is the function fromAdvSetWan of the file /goform/AdvSetWan of the component httpd. Executing a manipulation of the argument wanmode/PPPOEPassword can lead to buffer overflow. The attack can be launched remotely. The exploit has been publicly disclosed and may be utilized.
Tenda F453 routers are vulnerable to a remotely exploitable buffer overflow, allowing attackers to gain remote code execution (RCE). This vulnerability, triggered by manipulating the wanmode or PPPOEPassword arguments in the /goform/AdvSetWan function, could lead to complete system compromise and data exfiltration.
Step 1: Target Identification: The attacker identifies a vulnerable Tenda F453 router running firmware version 1.0.0.3, accessible via the internet.
Step 2: Payload Preparation: The attacker crafts a malicious HTTP POST request. This request targets the /goform/AdvSetWan endpoint. The request includes the wanmode or PPPOEPassword parameters, with values exceeding the allocated buffer size.
Step 3: Request Delivery: The attacker sends the crafted HTTP POST request to the vulnerable router.
Step 4: Vulnerability Trigger: The fromAdvSetWan function in the httpd process receives the malicious request and attempts to process the oversized wanmode or PPPOEPassword values.
Step 5: Buffer Overflow: The function copies the oversized input into a fixed-size buffer, causing a buffer overflow.
Step 6: Code Execution (Exploitation): The overflow overwrites critical memory regions, such as the return address. The attacker's crafted input includes shellcode or a pointer to shellcode. When the function returns, it jumps to the attacker-controlled code.
Step 7: Post-Exploitation: The attacker's shellcode executes, granting them remote code execution (RCE) on the router. This can lead to complete system compromise, including data exfiltration, device control, and network pivoting.
The vulnerability lies within the fromAdvSetWan function in the httpd component of the Tenda F453 router firmware. The function fails to properly validate the length of the wanmode and PPPOEPassword arguments received via an HTTP POST request. Specifically, the code likely copies the contents of these arguments into a fixed-size buffer without checking the input length. This leads to a buffer overflow when an attacker provides an overly long string for either of these parameters. The overflow overwrites adjacent memory, potentially allowing an attacker to overwrite critical data structures, including the return address, and redirect program execution to arbitrary code (e.g., shellcode) controlled by the attacker. The root cause is a lack of input validation and bounds checking on user-supplied data before it's copied into a fixed-size buffer. This allows for arbitrary code execution.