CVE-2021-24029: Facebook Mvfst

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a crash via a failed assertion. Per QUIC specification, this particular message should be treated as a connection error. This issue affects mvfst versions prior to commit a67083ff4b8dcbb7ee2839da6338032030d712b0 and proxygen versions prior to v2021.03.15.00.

Affected products

• Facebook Mvfst: before 2021-03-13 (fixed in 2021-03-13)
• Facebook Proxygen: before 2021.03.15.00 (fixed in 2021.03.15.00)

Published 2021-03-15. Last modified 2026-06-17.