GHSA-GQ9P-F254-H286 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...

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-CP4Q-FQW9-4HF6 Http4s Ember HTTP/2: unbounded continuation frame accumulation

When Ember receives an HTTP/2 HEADERS or PUSHPROMISE frame without the ENDHEADERS flag, it buffers the header block fragment and waits for subsequent CONTINUATION frames. These accumulate unbounded until the connection closes. Impact A remote, unauthenticated peer can exhaust the heap on any Embe...

Http4s Ember HTTP/2: unbounded continuation frame accumulation

When Ember receives an HTTP/2 HEADERS or PUSHPROMISE frame without the ENDHEADERS flag, it buffers the header block fragment and waits for subsequent CONTINUATION frames. These accumulate unbounded until the connection closes. Impact A remote, unauthenticated peer can exhaust the heap on any Embe...

GHSA-8F3Q-3JMV-7PRW Http4s Ember HTTP/2 has an unbounded outbound frame queue

Ember's HTTP/2 connection serializes all outgoing frames through a single unbounded queue drained by one writer fiber writeLoop. When the write side stalls, any frames the connection keeps producing accumulate in that queue without limit. The peer can drive this cheaply because the connection emi...

Http4s Ember HTTP/2 has an unbounded outbound frame queue

Ember's HTTP/2 connection serializes all outgoing frames through a single unbounded queue drained by one writer fiber writeLoop. When the write side stalls, any frames the connection keeps producing accumulate in that queue without limit. The peer can drive this cheaply because the connection emi...

GHSA-9VWC-PC8P-253Q Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS

An ember server with HTTP/2 enabled .withHttp2 does not enforce SETTINGSMAXCONCURRENTSTREAMS on streams opened by the peer. A single unauthenticated connection can open an unbounded number of concurrent streams, each of which allocates per-stream server state that is never released, exhausting th...

Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS

An ember server with HTTP/2 enabled .withHttp2 does not enforce SETTINGSMAXCONCURRENTSTREAMS on streams opened by the peer. A single unauthenticated connection can open an unbounded number of concurrent streams, each of which allocates per-stream server state that is never released, exhausting th...

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...

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...

EUVD-2026-79239

Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGSMAXFRAMESIZE. An unauthenticated peer can declare a payload near 16 MiB on a...

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-2026-88975 Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE

Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGSMAXFRAMESIZE. An unauthenticated peer can declare a payload near 16 MiB on a...

CVE-2026-69202 Http4s Ember HTTP/2: unbounded inbound body buffering

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...

CVE-2026-69202 Http4s Ember HTTP/2: unbounded inbound body buffering

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...

EUVD-2026-79234

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...

CVE-2026-69202

Http4s is a Scala HTTP services library. In versions prior to 0.23.35 and 1.0.0-M47 , Ember's HTTP/2 flow-control window is replenished based on bytes received from the network rather than bytes consumed by the application, and each stream stores DATA in an unbounded channel . A remote peer can t...

CVE-2026-69218 Http4s Ember HTTP/2: unbounded continuation frame accumulation

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, When Ember receives an HTTP/2 HEADERS or PUSHPROMISE frame without ENDHEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments without a size bound. A remote peer can keep an incomplete bloc...

CVE-2026-69218 Http4s Ember HTTP/2: unbounded continuation frame accumulation

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, When Ember receives an HTTP/2 HEADERS or PUSHPROMISE frame without ENDHEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments without a size bound. A remote peer can keep an incomplete bloc...

CVE-2026-69218

Http4s Ember HTTP/2 is vulnerable to unbounded continuation frame accumulation in its H2Connection component. When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without END_HEADERS, it buffers the header block and subsequent CONTINUATION fragments without a size bound . A remote peer can...