Http4s vulnerabilities

Http4s (Ember HTTP/1.1 module) prior to 0.23.35 and 1.0.0-M47 did not reject messages containing both Transfer-Encoding and Content-Length headers. This allows an intermediary and Ember to select different body framing rules, enabling HTTP request smuggling.

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 SETTINGS_MAX_FRAME_SIZE. An unauthenticated peer can declare a payload near 16 MiB on a connection where Ember advertised 16 KiB and either complete or slowly stream it, causing up to 1024-fold memory amplification per connection before processFrame can reject the frame. The shared H2Connection.readLoop affects withHttp2 servers and clients, while HTTP/2-disabled configurations are unaffected, and the patch rejects oversized frames before buffering their payloads. This issue is fixed in versions 0.23.37 and 1.0.0-M48.

Vulnerability in Http4s (a Scala interface for HTTP services) prior to 0.23.35 and 1.0.0-M47. When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without END_HEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments without a size bound, allowing a remote peer to exhaust heap memory.

Vulnerability in Http4s 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, enabling CL.CL request smuggling.

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, the CookieJar client middleware uses unanchored substring checks instead of RFC 6265 domain and path matching. Consequently, a cookie for example.com can be sent to an attacker-controlled hostname such as evilexample.com.

Vulnerability in Http4s prior to 0.23.35 and 1.0.0-M47. WebSocket FrameTranscoder.bodyLength rejects extended payload lengths above Integer.MAX_VALUE but permits negative 64-bit lengths, allowing a remote client to send a frame that causes an infinite decode loop and resource exhaustion.

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, DigestAuth replay protection records lastNc plus one instead of the highest nonce-count value it has accepted. When a legitimate client sends noncontiguous nc values due to parallel or retried requests, the stored counter remains below the accepted maximum, allowing a passive observer to replay a captured Authorization header multiple times.

Vulnerability in Http4s 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, leading to disagreement with RFC-compliant intermediaries and enabling TE.CL or TE.0 request smuggling.

In Http4s, an Ember server with HTTP/2 enabled does not enforce SETTINGS_MAX_CONCURRENT_STREAMS for peer-created streams. A single unauthenticated connection can open an unbounded number of streams, each retaining per-stream state until heap exhaustion. The same unchecked allocation is reachable in ember-client via server-initiated PUSH_PROMISE frames because enablePush is not enforced. Fixed in versions 0.23.35 and 1.0.0-M47.

In Http4s, Ember's HTTP/2 flow-control window is replenished based on 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 send a body faster than a slow or non-draining application consumes it, retaining payloads in heap on an ember-server or ember-client configured with withHttp2. The patch bounds the per-stream H2Connection body channel so application consumption applies backpressure. Fixed in versions 0.23.35 and 1.0.0-M47.

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 without re-encoding and interprets malformed chunk boundaries differently, an unauthenticated attacker can create TE.TE request smuggling that bypasses intermediary controls, poisons caches, or hijacks the request queue.

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, the CookieJar client middleware stores a response cookie's Domain attribute without checking that it domain-matches the host that supplied the cookie or rejecting public suffixes. A malicious or compromised server contacted through the same CookieJar can plant a cookie for another domain, and the jar later sends that cookie to the victim domain, enabling session fixation or overwriting security-sensitive cookies.

Http4s (versions prior to 0.23.35 and 1.0.0-M47) has a memory exhaustion vulnerability in the Ember HTTP/2 server. An unauthenticated HTTP/2 client can send PING, SETTINGS, or DATA frames that cause the server to enqueue acknowledgments or WINDOW_UPDATE frames faster than they are written, leading to heap memory exhaustion.

In Http4s, the FollowRedirect client middleware strips Authorization and Cookie headers only when a redirect changes authority, but authority comparison excludes the URI scheme. A same-authority redirect from HTTPS to HTTP therefore preserves credentials and transmits them over a plaintext connection.

In Http4s, ResponseCookie.render writes attacker-influenced name, content, domain, path, and extension values without neutralizing semicolons or control characters. An application that constructs a ResponseCookie from unvalidated input can emit injected cookie attributes such as Domain, Path, or SameSite, widening cookie scope or weakening protections, and control characters may enable header splitting.

Http4s (versions prior to 0.23.35 and 1.0.0-M47) has a memory exhaustion vulnerability in the shared WebSocket decoder. The decoder allows unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts declared lengths up to Int.MaxValue. A remote client that completes a WebSocket handshake can exhaust server memory.

Http4s (versions prior to 0.23.35 and 1.0.0-M47) has a memory exhaustion vulnerability in the DigestAuth server middleware. Due to an inverted stale-nonce comparison, the middleware does not remove fresh nonces and stops eviction at the first stale nonce. An unauthenticated attacker can repeatedly trigger authentication challenges, causing the persistent nonce map to grow until the JVM exhausts heap memory.

In Http4s, ResourceService and WebjarService decode each URL path segment but reject only segments exactly equal to an empty string, a dot, or two dots. A request containing percent-encoded slash or backslash separators can turn an accepted segment into a parent-directory traversal after decoding, allowing access to classpath or WebJar resources outside the configured base.

Http4s before versions 0.23.35 and 1.0.0-M47 has a DoS vulnerability via HTTP/2 in the Ember backend. The Hpack wrapper does not include indexed headers or per-header overhead in the header size limit, allowing a small block to expand into a large in-memory representation. Multiple malicious connections can exhaust process memory.

Http4s, a Scala interface for HTTP services, in versions from 1.0.0-M1 to before 1.0.0-M45 and before 0.23.31 is vulnerable to HTTP Request Smuggling due to improper handling of the HTTP trailer section. This could enable attackers to bypass front-end server security controls, launch targeted attacks against active users, and poison web caches. Exploitation requires the web application to be deployed behind a reverse-proxy that forwards trailer headers.