Arch Linux: Arbitrary code execution (CVE-2018-16839)

The internal function Curl_auth_create_plain_message fails to correctly verify that the passed in lengths for name and password aren't too long, then calculates a buffer size to allocate. On systems with a 32 bit size_t, the math to calculate the buffer size triggers an integer overflow when the user name length exceeds 2GB (2^31 bytes). This integer overflow usually causes a very small buffer to actually get allocated instead of the intended very huge one, making the use of that buffer end up in a heap buffer overflow.