CVE-2020-1888: Facebook Hhvm

High severity, CVSS 7.5. EPSS: 1.1% chance of exploitation in the next 30 days.

Insufficient boundary checks when decoding JSON in handleBackslash reads out of bounds memory, potentially leading to DOS. This issue affects HHVM 4.45.0, 4.44.0, 4.43.0, 4.42.0, 4.41.0, 4.40.0, 4.39.0, versions between 4.33.0 and 4.38.0 (inclusive), versions between 4.9.0 and 4.32.0 (inclusive), and versions prior to 4.8.7.

Affected products

• Facebook Hhvm: before 4.8.7 (fixed in 4.8.7); from 4.9.0, up to and including 4.32.0; from 4.33.0, up to and including 4.38.0; version 4.39.0 only; version 4.40.0 only; version 4.41.0 only; …

Published 2020-03-03. Last modified 2026-06-17.