Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS

SummaryThumbor's filters:convolution, , filter passes the user-controlled value to a C extension thumbor/ext/filters/convolution.c where it is used as a divisor for % and / without validating columns 0. When columns=0, the C code triggers undefined behavior; on x8664 this reliably results in a...