CVE-2026-44909: Facebook Proxygen

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Proxygen lacked a generalized slow-consumer detection mechanism in its core HTTP session layer. A remote, unauthenticated attacker could exploit HTTP/2 flow-control by setting SETTINGS_INITIAL_WINDOW_SIZE to 0 or withholding WINDOW_UPDATE frames, causing the server to buffer complete response bodies in memory indefinitely for stalled streams. By opening many simultaneous streams requesting large resources while preventing the server from transmitting responses, an attacker could induce unbounded memory growth leading to service degradation, resource exhaustion, or denial of service. Versions v2017.01.16.00 through v2026.07.20.00 are affected.

Affected products

• Facebook Proxygen: from v2017.01.16.00, before v2026.07.20.00 (fixed in v2026.07.20.00)

Published 2026-07-23. Last modified 2026-07-23.