CVE-2020-1919

Incorrect bounds calculations in substr_compare could lead to an
out-of-bounds read when the second string argument passed in is longer than
the first. This issue affects HHVM versions prior to 4.56.3, all versions
between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and
versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.