CVE-2026-69204 Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary...

CVE-2026-69204 Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary...

CVE-2026-69204 Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary...

CVE-2026-69217: Inconsistent Interpretation of HTTP Requests

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/1.1 parser accepts differing duplicate Content-Length headers and uses the last value instead of rejecting the message. When an Ember server is behind a keep-alive intermediary that selects a different...

PT-2026-92407

Name of the Vulnerable Software and Affected Versions Http4s versions prior to 0.23.35 Http4s versions prior to 1.0.0-M47 Description Ember's chunk decoder parses the chunk-size token leniently by trimming whitespace and accepting leading plus or minus signs, which deviates from the requirement f...

CVE-2026-88975: Uncontrolled Resource Consumption

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...

PT-2026-92405

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...

PT-2026-92428

When Ember receives an HTTP/2 HEADERS or PUSH PROMISE frame without the END HEADERS 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...

CVE-2026-69213: Uncontrolled Resource Consumption

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-2026-69205: Inconsistent Interpretation of HTTP Requests

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HeaderP.parse uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. Values such as Chunked are not recognized, values such as notchunke...

CVE-2026-69209: Uncontrolled Resource Consumption

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The shared WebSocket decoder permits unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts declared lengths up to Int.MaxValue. A remote client that...

CVE-2026-69202: Uncontrolled Resource Consumption

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...

PT-2026-92473

Name of the Vulnerable Software and Affected Versions Http4s versions prior to 0.23.37 Http4s versions prior to 1.0.0-M48 Description An issue exists in Ember's HTTP/2 read loop where the system parses a frame's 24-bit declared length but buffers the entire payload before comparing it with SETTIN...

PT-2026-92423

Summary Ember's HTTP/1.1 header parser matches the Transfer-Encoding header value with a case-sensitive substring test hValue.contains"chunked". RFC 9112 §7 requires transfer-coding names to be compared case-insensitively. A request carrying Transfer-Encoding: Chunked capital C is therefore not...

PT-2026-92427

Name of the Vulnerable Software and Affected Versions Http4s versions prior to 0.23.35 Http4s versions prior to 1.0.0-M47 Description Ember's HTTP/1.1 parser accepts duplicate Content-Length headers with different values and utilizes the last value instead of rejecting the message. This behavior...

CVE-2026-69204: Inconsistent Interpretation of HTTP Requests

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary...

PT-2026-92422

An ember server with HTTP/2 enabled .withHttp2 does not enforce SETTINGS MAX CONCURRENT STREAMS 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...

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...

CVE-2026-69216: Inconsistent Interpretation of HTTP Requests

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s chunk decoder trims the chunk-size token and accepts leading plus or minus signs instead of requiring one or more hexadecimal digits followed by the required CRLF. When an intermediary forwards chunked data...

PT-2026-92377

Summary Ember's HTTP/1.1 request parser does not reject a message that carries both a Transfer-Encoding and a Content-Length header. RFC 9112 §6.1 requires a server to treat such a message as a framing error and close the connection. An intermediary that follows the RFC's CL-strip-and-forward pat...