CVE-2019-11930: Facebook Hhvm

Critical severity, CVSS 9.8. EPSS: 3.2% chance of exploitation in the next 30 days.

An invalid free in mb_detect_order can cause the application to crash or potentially result in remote code execution. This issue affects HHVM versions prior to 3.30.12, all versions between 4.0.0 and 4.8.5, all versions between 4.9.0 and 4.23.1, as well as 4.24.0, 4.25.0, 4.26.0, 4.27.0, 4.28.0, and 4.28.1.

Affected products

• Facebook Hhvm: before 3.30.12 (fixed in 3.30.12); from 4.0.0, up to and including 4.8.5; from 4.9.0, up to and including 4.23.1; version 4.24.0 only; version 4.25.0 only; version 4.26.0 only; …

Published 2019-12-04. Last modified 2026-06-17.