CVE-2021-24036: Facebook Folly

Critical severity, CVSS 9.8. EPSS: 3.3% chance of exploitation in the next 30 days.

Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with the possibility of remote code execution. This issue affects versions of folly prior to v2021.07.22.00. This issue affects HHVM versions prior to 4.80.5, all versions between 4.81.0 and 4.102.1, all versions between 4.103.0 and 4.113.0, and versions 4.114.0, 4.115.0, 4.116.0, 4.117.0, 4.118.0 and 4.118.1.

Affected products

• Facebook Folly: before 2021.07.22.00 (fixed in 2021.07.22.00)
• Facebook Hhvm: before 4.80.5 (fixed in 4.80.5); from 4.81.0, up to and including 4.102.1; from 4.103.0, up to and including 4.113.0; version 4.114.0 only; version 4.115.0 only; version 4.116.0 only; …

Published 2021-07-23. Last modified 2026-06-17.