CVE-2026-71942: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in DrayTek Corporation VigorSwitch G2540xs

CVE-2026-71942 describes a classic buffer overflow vulnerability in the mail_mailalert function of DrayTek VigorSwitch G2540xs. The vulnerability arises because multiple smtpReceiver email addresses are concatenated into a fixed-size buffer without checking the remaining buffer size, allowing a remote attacker with administrative privileges to trigger a buffer overflow. This can cause denial of service or potentially allow execution of arbitrary commands on the device. The vulnerability requires authenticated access to the device's web management interface. No patch or official remediation has been disclosed as of the published date.

Successful exploitation can cause denial of service or potentially enable arbitrary command execution on affected devices. However, exploitation requires valid administrative credentials, limiting the attack surface to authorized users. There are no known exploits in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict administrative access to trusted personnel only and monitor for suspicious activity on the device's management interface.