CVE-2026-71941: Buffer Copy without Checking Size of Input

Multiple DrayTek VigorSwitch models contain a buffer overflow vulnerability in the diag_logmail function. The vulnerability is caused by concatenating multiple smtpReceiver email addresses into a fixed-size buffer without checking the remaining buffer size. A remote attacker can trigger this vulnerability via crafted input, causing a denial of service or potentially executing arbitrary commands. Exploitation requires valid administrative credentials for the device's web management interface.