CURL-CVE-2016-8617

OOB write via unchecked multiplication

In libcurl's base64 encode function, the output buffer is allocated as follows without any checks on `insize`: malloc( insize * 4 / 3 + 4 ) On systems with 32-bit addresses in userspace (e.g. x86, ARM, x32), the multiplication in the expression wraps around if `insize` is at least 1GB of data. If this happens, an undersized output buffer is allocated, but the full result is written, thus causing the memory behind the output buffer to be overwritten. If a username is set directly via `CURLOPT_USERNAME` (or curl's `-u, --user` option), this vulnerability can be triggered. The name has to be at least 512MB big in a 32-bit system. Systems with 64-bit versions of the `size_t` type are not affected by this issue.