The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.

grpc-swift is the Swift language implementation of gRPC, a remote procedure call (RPC) framework. Prior to version 1.7.2, a grpc-swift server is vulnerable to a denial of service attack via a reachable assertion. This is due to incorrect logic when handling GOAWAY frames. The attack is low-effort: it takes very little resources to construct and send the required sequence of frames. The impact on availability is high as the server will crash, dropping all in flight connections and requests. This issue is fixed in version 1.7.2. There are currently no known workarounds.

Mismanaged state in GRPCWebToHTTP2ServerCodec.swift in gRPC Swift 1.1.0 and 1.1.1 allows remote attackers to deny service by sending malformed requests.

LengthPrefixedMessageReader in gRPC Swift 1.1.0 and earlier allocates buffers of arbitrary length, which allows remote attackers to cause uncontrolled resource consumption and deny service.

HTTP2ToRawGRPCServerCodec in gRPC Swift 1.1.1 and earlier allows remote attackers to deny service via the delivery of many small messages within a single HTTP/2 frame, leading to Uncontrolled Recursion and stack consumption.