Critical Vulnerability Information Affected Product Vendor: Tenda (Shenzhen Tenda Technology Co., Ltd.) Product: Tenda A21 Affected Version: Firmware V1.0.0.0 Vulnerability Type: Stack-based Buffer Overflow (Binary) Vulnerability Description During a security review of the Tenda A21 router firmware (version V1.0.0.0), a critical stack-based buffer overflow vulnerability was discovered in the Wi-Fi configuration endpoint . Vulnerability Cause The vulnerability arises from unsafe string operations during the device's processing of 5GHz SSID generation logic. Impact Remote Code Execution (RCE): By hijacking the stored program counter (PC/return address) on the stack, attackers can redirect execution to malicious payloads or ROP chains. Denial of Service (DoS): Corrupting the stack structure causes the httpd process to crash, rendering the device management interface unavailable. Code Vulnerability Example (C Language Representation): Remediation Recommendations 1. Use Safe Functions: Replace with to ensure output never exceeds the target buffer size. 2. Input Validation: Enforce a maximum length for the parameter at the function entry point.