CVE-2026-69202: HTTP4S

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

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/2 flow-control window is replenished according to bytes received from the network rather than bytes consumed by the application, while each stream stores DATA in an unbounded channel. A hostile peer can therefore send a body faster than a slow or non-draining application consumes it, retaining payloads in heap on an ember-server or ember-client configured with withHttp2. The patch bounds the per-stream H2Connection body channel so application consumption applies backpressure. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Affected products

• HTTP4S HTTP4S: before 0.23.35 (fixed in 0.23.35); from 1.0.0-M1, before 1.0.0-M47 (fixed in 1.0.0-M47)

Published 2026-09-15. Last modified 2026-09-16.