An issue was discovered on certain DrayTek Vigor routers before July 2022 such as the Vigor3910 before 4.3.1.1. /cgi-bin/wlogin.cgi has a buffer overflow via the username or password to the aa or ab field.

DrayTek Vigor310 devices through 4.3.2.6 allow a remote attacker to execute arbitrary code via the function ftpayloaddns(), because a byte sign-extension operation occurs for the length argument of a memcpy call, leading to a heap-based Buffer Overflow.

DrayTek Vigor3910 devices through 4.3.2.6 have a stack-based overflow when processing query string parameters because GetCGI mishandles extraneous ampersand characters and long key-value pairs.

Several CGI endpoints are vulnerable to buffer overflows, by authenticated users, because of missing bounds checking on parameters passed through POST requests to the strcpy function on DrayTek Vigor310 devices through 4.3.2.6.

Buffer Overflow vulnerabilities exist in DrayTek Vigor310 devices through 4.3.2.6 (in the Vigor management UI) because of improper retrieval and handling of the CGI form parameters.

The CGI endpoints v2x00.cgi and cgiwcg.cgi of DrayTek Vigor3910 devices through 4.3.2.6 are vulnerable to buffer overflows, by authenticated users, because of missing bounds checking on parameters passed through POST requests to the strncpy function.

An issue in DrayTek Vigor310 devices through 4.3.2.6 allows an attacker to obtain sensitive information because the httpd server of the Vigor management UI uses a static string for seeding the PRNG of OpenSSL.

DrayTek Vigor3910 devices through 4.3.2.6 allow unauthenticated DOM-based reflected XSS.

Stored XSS, by authenticated users, is caused by poor sanitization of the Login Page Greeting message in DrayTek Vigor310 devices through 4.3.2.6.