Last updated 24 February 2025
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.
End of life: 5/29/2024, Latest version: 1.25.5
End of life: 5/29/2024, Latest version: 1.25.5
End of life: 4/23/2024, Latest version: 1.24.0
End of life: 4/23/2024, Latest version: 1.24.0
NGINX Open Source before versions 1.23.2 and 1.22.1, NGINX Open Source Subscription before versions R2 P1 and R1 P1, and NGINX Plus before versions R27 P1 and R26 P1 have a vulnerability in the module ngxhttpmp4module that might allow a local attacker to cause a worker process crash, or might result in worker process memory disclosure by using a specially crafted audio or video file. The issue affects only NGINX products that are built with the module ngxhttpmp4module, when the mp4 directive is used in the configuration file. Further, the attack is possible only if an attacker can trigger processing of a specially crafted audio or video file with the module ngxhttpmp4module.
NGINX Open Source before versions 1.23.2 and 1.22.1, NGINX Open Source Subscription before versions R2 P1 and R1 P1, and NGINX Plus before versions R27 P1 and R26 P1 have a vulnerability in the module ngxhttpmp4module that might allow a local attacker to corrupt NGINX worker memory, resulting in its termination or potential other impact using a specially crafted audio or video file. The issue affects only NGINX products that are built with the ngxhttpmp4module, when the mp4 directive is used in the configuration file. Further, the attack is possible only if an attacker can trigger processing of a specially crafted audio or video file with the module ngxhttpmp4module.
End of life: 4/11/2023, Latest version: 1.22.1
End of life: 4/11/2023, Latest version: 1.22.1
ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.
NGINX before 1.13.6 has a buffer overflow for years that exceed four digits, as demonstrated by a file with a modification date in 1969 that causes an integer overflow (or a false modification date far in the future), when encountered by the autoindex module.
End of life: 6/21/2022, Latest version: 1.21.6
End of life: 6/21/2022, Latest version: 1.21.6
A flaw was found in nginx. An off-by-one error while processing DNS responses allows a network attacker to write a dot character out of bounds in a heap allocated buffer which can allow overwriting the least significant byte of next heap chunk metadata likely leading to a remote code execution in certain circumstances. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
End of life: 5/24/2022, Latest version: 1.20.2
End of life: 5/24/2022, Latest version: 1.20.2
End of life: 4/20/2021, Latest version: 1.18.0
End of life: 4/20/2021, Latest version: 1.18.0
IDE Xcode Server. Multiple issues were addressed by updating nginx to version 1.21.0.
nginx http proxy module does not verify peer identity of https origin server which could facilitate man-in-the-middle attack (MITM)
A flaw was found in HTTP/2. An attacker can request a large amount of data by manipulating window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queued, this queue can consume excess CPU, memory, or both, leading to a denial of service. The highest 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 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.
End of life: 4/20/2020, Latest version: 1.16.1
End of life: 4/20/2020, Latest version: 1.16.1
IDE Xcode Server. Multiple issues were addressed by updating nginx to version 1.21.0.
IDE Xcode Server. Multiple issues were addressed by updating nginx to version 1.21.0.
IDE Xcode Server. Multiple issues were addressed by updating nginx to version 1.21.0.
End of life: 4/23/2019, Latest version: 1.14.2