Breaking something is easier than protecting everything from all fronts.
Hackers write the worst code, but all the mess needs only one successful hit to become a 0day.
Hackers write the worst code, but all the mess needs only one successful hit to become a 0day.
For example, look at the glibc/iconv CVE some other user posted[1]. In the section "Out-of-bound write when converting to ISO-2022-CN-EXT" they have mapped out the boundary checks. By diagnosing the problem this detailed, they already did 90% of the work. The other 10% are the patch and writing to the mailing list.
Surely someone doing all this would already have submitted a patch if they felt comfortable.