CVE-2020-1919: Facebook Hhvm

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

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.

Affected products

• Facebook Hhvm: before 4.56.3 (fixed in 4.56.3); from 4.57.0, before 4.80.2 (fixed in 4.80.2); from 4.81.0, before 4.93.2 (fixed in 4.93.2); version 4.94.0 only; version 4.95.0 only; version 4.96.0 only; …

Published 2021-03-10. Last modified 2026-06-17.