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.

When an HTTP/2 profile is configured on a virtual server, undisclosed requests can cause an increase in memory resource utilization.

Impact: System performance can degrade until the TMM process is either forced to restart or is manually restarted. This vulnerability allows a remote, unauthenticated attacker to cause a degradation of service that can lead to a denial-of-service (DoS) on the BIG-IP system. There is no control plane exposure; this is a data plane issue only.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

When SSL profiles are configured on a virtual server, undisclosed traffic can cause the virtual server to stop processing new client connections.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

When an SSL profile is configured on a virtual server on BIG-IP Virtual Edition (VE) without Intel QuickAssist Technology (QAT) or on BIG-IP hardware platforms with the database variable crypto.hwacceleration set to disabled, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

When HTTP/2 is configured on BIG-IP or BIG-IP Next SPK systems, undisclosed responses can cause the Traffic Management Microkernel (TMM) to terminate.

When Diffie-Hellman (DH) group Elliptic Curve Cryptography (ECC) Brainpool curves are configured in an SSL profile's Cipher Rule or Cipher Group, and that profile is applied to a virtual server, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate.

When a TCP profile with Multipath TCP (MPTCP) enabled is configured on a virtual server, undisclosed traffic along with conditions beyond the attacker's control can cause the Traffic Management Microkernel (TMM) to terminate.

When an iRule containing the HTTP::respond command is configured on a virtual server, undisclosed requests can cause an increase in memory resource utilization.

On BIG-IP Next CNF, BIG-IP Next SPK, and BIG-IP Next for Kubernetes systems, repeated undisclosed API calls can cause the Traffic Management Microkernel (TMM) to terminate.

When HTTP/2 Ingress is configured, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate.

When a client SSL profile is configured on a virtual server, undisclosed requests can cause an increase in memory resource utilization.

When using a multi-bladed platform with more than one active blade, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate.

An HTTP/2 implementation flaw allows a denial-of-service (DoS) that uses malformed HTTP/2 control frames in order to break the max concurrent streams limit (HTTP/2 MadeYouReset Attack).

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

When a Stream Control Transmission Protocol (SCTP) profile is configured on a virtual server, undisclosed requests can cause an increase in memory resource utilization.

The BGP daemon (bgpd) in IP Infusion ZebOS through 7.10.6 allow remote attackers to cause a denial of service by sending crafted BGP update messages containing a malformed attribute.

When a TCP profile with Multipath TCP enabled (MPTCP) is configured on a virtual server, undisclosed traffic along with conditions beyond the attacker's control can cause the Traffic Management Microkernel (TMM) to terminate.