CVE-2019-11929: Facebook Hhvm

Critical severity, CVSS 9.8. EPSS: 4% chance of exploitation in the next 30 days.

Insufficient boundary checks when formatting numbers in number_format allows read/write access to out-of-bounds memory, potentially leading to remote code execution. This issue affects HHVM versions prior to 3.30.10, all versions between 4.0.0 and 4.8.5, all versions between 4.9.0 and 4.18.2, and versions 4.19.0, 4.19.1, 4.20.0, 4.20.1, 4.20.2, 4.21.0, 4.22.0, 4.23.0.

Affected products

• Facebook Hhvm: before 3.30.10 (fixed in 3.30.10); from 4.0.0, up to and including 4.8.5; from 4.9.0, up to and including 4.18.2; version 4.19.0 only; version 4.19.1 only; version 4.20.0 only; …

Published 2019-10-02. Last modified 2026-06-17.