CVE-2026-69203

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, An Ember server with HTTP/2 enabled through withHttp2 does not enforce SETTINGSMAXCONCURRENTSTREAMS for peer-created streams. One unauthenticated connection can open an unbounded number of streams, each retaining...

CVE-2026-69202

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...

Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE

Summary An unauthenticated peer can make Ember's HTTP/2 read loop hold 16 MiB of a single frame in memory on a connection where Ember advertised a 16 KiB limit. The declared length is readable from the frame's first 9 bytes, but it is not compared against SETTINGSMAXFRAMESIZE until the whole...

GHSA-6M4X-PP6Q-5JMM Http4s Ember HTTP/2: unbounded inbound body buffering

Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore provides no backpressure: a peer can stream a large or unbounded body...

CVE-2026-88975

Http4s (a Scala HTTP library) is vulnerable in Ember's HTTP/2 read loop prior to versions 0.23.37 and 1.0.0-M48 . The loop parses a frame's 24-bit declared length but buffers the entire payload before comparing it against SETTINGS_MAX_FRAME_SIZE . An unauthenticated peer can declare a payload nea...

CVE-2026-69213 Http4s Ember HTTP/2: unbounded outbound frame queue

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause...

CVE-2026-69213 Http4s Ember HTTP/2: unbounded outbound frame queue

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause...

EUVD-2026-79183

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause...

PT-2026-92421

Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore provides no backpressure: a peer can stream a large or unbounded body...