CVE-2018-6335: Facebook Hhvm

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

A Malformed h2 frame can cause 'std::out_of_range' exception when parsing priority meta data. This behavior can lead to denial-of-service. This affects all supported versions of HHVM (3.25.2, 3.24.6, and 3.21.10 and below) when using the proxygen server to handle HTTP2 requests.

Affected products

• Facebook Hhvm: up to and including 3.21.10; version 3.24.6 only; version 3.25.2 only

Published 2018-12-31. Last modified 2026-06-17.