Tenda RX3 Router Wi-Fi Schedule Buffer Overflow Vulnerability Analysis

Critical Vulnerability Information Affected Product Vendor: Tenda (Shenzhen Tenda Technology Co., Ltd.) Product: Tenda RX3 Affected Version: Firmware V16.03.13.11 Vulnerability Details Type: Buffer Overflow (Binary) Affected Interface: Wi-Fi schedule configuration ( ) Vulnerability Description During a security review, a critical buffer overflow vulnerability was discovered in the Wi-Fi scheduling configuration endpoint of the Tenda RX3 router firmware (version V16.03.13.11). The vulnerability resides in the function, which retrieves user-controlled parameters and via the interface. These values are copied into a heap-allocated buffer of fixed size (25 bytes) using the unsafe function. Due to the lack of input length validation, an attacker can supply an excessively long string to overflow the buffer, leading to memory corruption, denial of service (DoS), or potentially arbitrary code execution. Root Cause Analysis Fixed Allocation: The function allocates a 25-byte buffer on the heap using . Unsafe Copying: The code uses and to copy and values. Exploitation: An attacker can provide a parameter significantly longer than the allocated space, causing a buffer overflow that corrupts heap memory and adjacent structures, or triggers crashes or control flow hijacking during other stack operations in the function logic. Vulnerable Code Logic Impact Denial of Service (DoS): Memory corruption will cause the process to crash, rendering the device management interface unavailable. Remote Code Execution (RCE): With careful manipulation of the overflow, an attacker may hijack the application’s control flow. Vulnerability Verification Example (Python Script) Demonstrates how to trigger the overflow by sending a crafted payload. Other Verification Methods Firmware emulation successfully executed; the vulnerability can be triggered in a simulated environment with access to the web interface. Mitigation Measures 1. Use Safe Functions: Replace with , ensuring the copied length does not exceed the remaining buffer capacity. 2. Pre-copy Validation: Implement strict validation for time-related strings (e.g., ensure they follow "HHMM" format and are no longer than 4–5 characters). 3. Buffer Management: Ensure allocated memory is sufficient to hold all possible valid inputs plus a null terminator.

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Tenda RX3 Router Wi-Fi Schedule Buffer Overflow Vulnerability Analysis

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