CVE-2026-69205

Http4s (a Scala HTTP library) is affected in its Ember backend, specifically the HeaderP.parse function, which uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. This causes mismatches with RFC-compliant intermediaries,...

CVE-2026-69213

Http4s is a Scala interface for HTTP services. The vulnerability lies in Ember HTTP/2 , which serializes outbound frames through a single unbounded queue consumed by writeLoop. When a peer stops reading, an unauthenticated HTTP/2 client can keep sending PING, SETTINGS, or DATA frames , causing Em...

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-2026-69216 Http4s: Ember chunk parser lenience (TE.TE request smuggling)

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...

CVE-2026-69216

Http4s is a Scala library for HTTP services. Prior to 0.23.35 and 1.0.0-M47 , the Ember chunk decoder accepted leading plus or minus signs in the chunk-size token instead of requiring one or more hexadecimal digits followed by CRLF. This leniency allows an unauthenticated attacker to construct TE...

EUVD-2026-79176

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...

CVE-2026-69204

CVE-2026-69204 affects Http4s , a Scala HTTP library, specifically the Ember HTTP/1.1 implementation. The root cause is that Ember does not reject messages containing both Transfer-Encoding and Content-Length headers, allowing an intermediary and Ember to select different body framing rules. This...

EUVD-2026-79025

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...

Improper Handling of Highly Compressed Data (Data Amplification)

Overview Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data Data Amplification through the Hpack.decodeHeaders path in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala. An attacker can exhaust heap memory and crash an HTTP/2 server...

Improper Handling of Highly Compressed Data (Data Amplification)

Overview Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data Data Amplification through the Hpack.decodeHeaders path in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala. An attacker can exhaust heap memory and crash an HTTP/2 server...

Improper Handling of Highly Compressed Data (Data Amplification)

Overview Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data Data Amplification through the Hpack.decodeHeaders path in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala. An attacker can exhaust heap memory and crash an HTTP/2 server...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling due to improper parsing of the HTTP trailer section in the parse function. An attacker can bypass security controls, launch targeted attacks against users, or poison web caches by crafting specially formed HTTP...

Unbounded connection acceptance in http4s-blaze-server

Impact blaze-core, a library underlying http4s-blaze-server, accepts connections unboundedly on its selector pool. This has the net effect of amplifying degradation in services that are unable to handle their current request load, since incoming connections are still accepted and added to an...