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...

CVE-2026-54556

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

GHSA-VMM3-XGCX-67HM http4s has HTTP/2 Denial of Service with Ember Backend

Summary http4s 0.23.x and 1.0 servers running ember with http2 enabled are vulnerable to a denial of service attack using a HPACK bomb vulnerability recently disclosed as affecting other http2 servers. Impact Denial of Service: - Affects any http4s server running the ember backend with HTTP/2...

http4s has HTTP/2 Denial of Service with Ember Backend

Summary http4s 0.23.x and 1.0 servers running ember with http2 enabled are vulnerable to a denial of service attack using a HPACK bomb vulnerability recently disclosed as affecting other http2 servers. Impact Denial of Service: - Affects any http4s server running the ember backend with HTTP/2...

CVE-2026-54556 Http4s: HTTP/2 Denial of Service with Ember Backend

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

CVE-2026-54556 Http4s: HTTP/2 Denial of Service with Ember Backend

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

CVE-2026-54556 Http4s: HTTP/2 Denial of Service with Ember Backend

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

CVE-2026-54556

http4s (Scala HTTP library) versions prior to 0.23.35 and 1.0.0-M47 are vulnerable to an out-of-memory denial of service when using the Ember backend with HTTP/2 enabled. The root cause is a HPACK bomb : the Hpack wrapper concatenates HEADERS and CONTINUATION frame fragments into a single decoded...

EUVD-2026-66558

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

CVE-2026-54556: Improper Handling of Highly Compressed Data (Data Amplification)

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala...

PT-2026-82110

Name of the Vulnerable Software and Affected Versions Http4s versions prior to 0.23.35 Http4s versions prior to 1.0.0-M47 Description An unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend when HTTP/2 is enabled. The issue resides in the Hpack wrapper...

CVE-2026-73493

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

EUVD-2026-57631

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

CVE-2026-73493

Summary: The CVE affects http4s-blaze-server in WebSocket handling where fragmented messages can be aggregated without an upper bound, causing unbounded heap growth and potential DoS via OutOfMemoryError on the Blaze server thread. Affected scope: any http4s application serving WebSocket routes o...

CVE-2026-73493 http4s-blaze-server: Unbounded WebSocket message aggregation

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

CVE-2026-73493 http4s-blaze-server: Unbounded WebSocket message aggregation

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

CVE-2026-73493 http4s-blaze-server: Unbounded WebSocket message aggregation

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

CVE-2026-73493

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...

PT-2026-71347

Name of the Vulnerable Software and Affected Versions http4s-blaze-server versions prior to 0.23.18 http4s-blaze-server versions prior to 1.0.0-M42 Description The software aggregates fragments of incoming WebSocket messages without limiting the total size or the number of fragments. A client can...

CVE-2026-73493: Allocation of Resources Without Limits or Throttling

Http4s http4s-blaze-server is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an...