curl: Integer-underflow leads to heap over-read in TFTP implementation

libcurl on commit 3ee1d3b573e6ea36fb478dbd0d9913483b900928 contains a vulnerability in its TFTP implementation that can cause curl or a libcurl-user to send heap memory beyond the bounds of an allocated chunk to a malicious TFTP server. The vulnerability lies in lib/tftp.c, in function...