HTTP/2 Rapid reset attack The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RSTSTREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RSTSTREAM frame, before any other data from that TCP connection is processed.

Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RSTSTREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.

The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.

The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.

In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RSTSTREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.

Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the swift-nio-http2 repo advisory and their original conent follows.

swift-nio-http2 specific advisory swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new Channels to serve the traffic. This can easily overwhelm an EventLoop and prevent it from making forward progress.

swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.

Uncontrolled Resource Consumption vulnerability in Apache Traffic Server.

This issue affects Apache Traffic Server: from 9.0.0 through 9.1.13, from 10.0.0 through 10.1.2.

Users are recommended to upgrade to version 9.1.14 or 10.1.3, which fixes the issue.

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Traffic Server.

This issue affects Apache Traffic Server: from 10.0.0 through 10.1.3, from 9.0.0 through 9.2.14.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fixes the issue.

Regular Expression without Anchors vulnerability in Apache Traffic Server.

This issue affects Apache Traffic Server: from 10.0.X through 10.1.3, from 9.0.X through 9.2.14.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fixes the issue.

Improper Input Validation vulnerability in Apache Traffic Server.

This issue affects Apache Traffic Server: from 9.2.0 through 9.2.14, from 10.1.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fixes the issue.

A flaw was found in HTTP/2. Using SETTINGS frames and queuing of SETTINGS ACK frames, a flood could occur resulting in unbounded memory growth. The highest threat from this vulnerability is to system availability.

A flaw was found in HTTP/2. An attacker, using PRIORITY frames to flood the system, could cause excessive CPU usage and starvation of other clients. The largest threat from this vulnerability is to system availability.

A flaw was found in HTTP/2. An attacker, sending a stream of header with a 0-length header name and a 0-length header value, could cause some implementations to allocate memory for these headers and keep the allocations alive until the session dies. The can consume excess memory, potentially leading to a denial of service. The highest threat from this vulnerability is to system availability.

A vulnerability was found in http/2 where an attacker opens the HTTP/2 window so the peer can send without constraint; however, they leave the TCP window closed so the peer cannot actually write (many of) the bytes on the wire. The attacker then sends a stream of requests for a large response object. Depending on how the servers queue the responses, this can consume excess memory, CPU, or both, potentially leading to a denial of service.

Apache Traffic Server can reuse server sessions and tunnels improperly, exposing data across client connections.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server mishandles PROXY protocol input, truncating ports and overflowing the stack.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server can bypass IP access controls on UDS listeners and through ACL matching errors.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server reads out of bounds while parsing DNS answers.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server can crash from null dereferences and dangling references in TLS and SNI handling.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

The Apache Traffic Server certifier plugin generates certificates based on attacker-controlled client SNI.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server mishandles on-disk cache fields and object lifetimes, corrupting state or crashing.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server has use-after-free and time-of-check/time-of-use errors in remap configuration handling.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server updates the HTTP/2 HPACK dynamic table before confirming the header block encoded successfully, so an encode failure leaves the encoder out of sync with the peer decoder and corrupts subsequent header blocks on the connection.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server copies the client Host header into a fixed-size stack buffer without a bound during redirect handling, so an over-long Host header overflows the stack when redirect following is enabled.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Improper Access Control vulnerability in Apache Traffic Server.

This issue affects Apache Traffic Server: from 9.0.0 through 9.1.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.1.15 or 10.1.4, which fixes the issue.

Apache Traffic Server allows request smuggling if chunked messages are malformed.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server does not reject Transfer-Encoding in HTTP/2 requests, allowing downgrade request smuggling.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server can be crashed or driven to resource exhaustion by abusive HTTP/2 framing and flow-control.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server mishandles integers while decoding HPACK/XPACK headers, corrupting memory.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server forwards HTTP/2 origin trailers to HTTP/1 clients without proper chunked framing when converting HTTP/2 to HTTP/1.

This issue affects Apache Traffic Server: from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server can write out of bounds or overflow integers while parsing MIME and HTTP headers.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server truncates over-long header names, allowing header aliasing, request smuggling, and policy bypass.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server mis-parses ports in URLs and userinfo, allowing port-based access-control bypass.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server drops the per-stream buffer cap when dechunking HTTP/2 or HTTP/3 responses, letting a slow client exhaust server memory.

This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.

Apache Traffic Server reuses multiplexed HTTP/2 origin connections without verifying the server certificate covers the new request hostname.

This issue affects Apache Traffic Server: from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.

Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.