Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. When parsing a spoofed TLS handshake message, picotls (specifically, bindings within picotls that call the crypto libraries) may attempt to free the same memory twice. This double free occurs during the disposal of multiple objects without any intervening calls to malloc Typically, this triggers the malloc implementation to detect the error and abort the process. However, depending on the internals of malloc and the crypto backend being used, the flaw could potentially lead to a use-after-free scenario, which might allow for arbitrary code execution. The vulnerability is addressed with commit 9b88159ce763d680e4a13b6e8f3171ae923a535d.

Buffer overflow in H2O version 2.2.4 and earlier allows remote attackers to execute arbitrary code or cause a denial of service (DoS) via unspecified vectors.

Use-after-free vulnerability in H2O allows remote attackers to cause a denial-of-service (DoS) or obtain server certificate private keys and possibly other information.

H2O is an HTTP server. In versions 2.3.0-beta2 and prior, when the reverse proxy handler tries to processes a certain type of invalid HTTP request, it tries to build an upstream URL by reading from uninitialized pointer. This behavior can lead to crashes or leak of information to back end HTTP servers. Pull request number 3229 fixes the issue. The pull request has been merged to the master branch in commit f010336. Users should upgrade to commit f010336 or later.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When an HTTP request using TLS/1.3 early data on top of TCP Fast Open or QUIC 0-RTT packets is received and the IP-address-based access control is used, the access control does not detect and prohibit HTTP requests conveyed by packets with a spoofed source address. This behavior allows attackers on the network to execute HTTP requests from addresses that are otherwise rejected by the address-based access control. The vulnerability has been addressed in commit 15ed15a. Users may disable the use of TCP FastOpen and QUIC to mitigate the issue.

Quicly is an IETF QUIC protocol implementation. Quicly up to commtit d720707 is susceptible to a denial-of-service attack. A remote attacker can exploit these bugs to trigger an assertion failure that crashes process using quicly. The vulnerability is addressed with commit 2a95896104901589c495bc41460262e64ffcad5c.

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.

H2O versions 2.0.3 and earlier and 2.1.0-beta2 and earlier allows remote attackers to cause a denial-of-service (DoS) via format string specifiers in a template file via fastcgi, mruby, proxy, redirect or reproxy.

H2O version 2.2.3 and earlier allows remote attackers to cause a denial of service in the server via specially crafted HTTP/2 header.

lib/http2/connection.c in H2O before 1.7.3 and 2.x before 2.0.0-beta5 mishandles HTTP/2 disconnection, which allows remote attackers to cause a denial of service (use-after-free and application crash) or possibly execute arbitrary code via a crafted packet.

H2O version 2.2.2 and earlier allows remote attackers to cause a denial of service in the server via specially crafted HTTP/1 header.

Buffer overflow in H2O version 2.2.2 and earlier allows remote attackers to cause a denial-of-service in the server via unspecified vectors.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. The QUIC stack (quicly), as used by H2O up to commit 43f86e5 (in version 2.3.0-beta and prior), is susceptible to a state exhaustion attack. When H2O is serving HTTP/3, a remote attacker can exploit this vulnerability to progressively increase the memory retained by the QUIC stack. This can eventually cause H2O to abort due to memory exhaustion. The vulnerability has been resolved in commit d67e81d03be12a9d53dc8271af6530f40164cd35. HTTP/1 and HTTP/2 are not affected by this vulnerability as they do not use QUIC. Administrators looking to mitigate this issue without upgrading can disable HTTP/3 support.

h2o is an open source http server. In code prior to the 8c0eca3 commit h2o may attempt to access uninitialized memory. When receiving QUIC frames in certain order, HTTP/3 server-side implementation of h2o can be misguided to treat uninitialized memory as HTTP/3 frames that have been received. When h2o is used as a reverse proxy, an attacker can abuse this vulnerability to send internal state of h2o to backend servers controlled by the attacker or third party. Also, if there is an HTTP endpoint that reflects the traffic sent from the client, an attacker can use that reflector to obtain internal state of h2o. This internal state includes traffic of other connections in unencrypted form and TLS session tickets. This vulnerability exists in h2o server with HTTP/3 support, between commit 93af138 and d1f0f65. None of the released versions of h2o are affected by this vulnerability. There are no known workarounds. Users of unreleased versions of h2o using HTTP/3 are advised to upgrade immediately.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. In version 2.3.0-beta2 and prior, when h2o is configured to listen to multiple addresses or ports with each of them using different backend servers managed by multiple entities, a malicious backend entity that also has the opportunity to observe or inject packets exchanged between the client and h2o may misdirect HTTPS requests going to other backends and observe the contents of that HTTPS request being sent.

The attack involves a victim client trying to resume a TLS connection and an attacker redirecting the packets to a different address or port than that intended by the client. The attacker must already have been configured by the administrator of h2o to act as a backend to one of the addresses or ports that the h2o instance listens to. Session IDs and tickets generated by h2o are not bound to information specific to the server address, port, or the X.509 certificate, and therefore it is possible for an attacker to force the victim connection to wrongfully resume against a different server address or port on which the same h2o instance is listening.

Once a TLS session is misdirected to resume to a server address / port that is configured to use an attacker-controlled server as the backend, depending on the configuration, HTTPS requests from the victim client may be forwarded to the attacker's server.

An H2O instance is vulnerable to this attack only if the instance is configured to listen to different addresses or ports using the listen directive at the host level and the instance is configured to connect to backend servers managed by multiple entities.

A patch is available at commit 35760540337a47e5150da0f4a66a609fad2ef0ab. As a workaround, one may stop using using host-level listen directives in favor of global-level ones.

H2O version 2.2.3 and earlier allows remote attackers to cause a denial of service in the server via unspecified vectors.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. The configuration directives provided by the headers handler allows users to modify the response headers being sent by h2o. The configuration file of h2o has scopes, and the inner scopes (e.g., path level) are expected to inherit the configuration defined in outer scopes (e.g., global level). However, if a header directive is used in the inner scope, all the definition in outer scopes are ignored. This can lead to headers not being modified as expected. Depending on the headers being added or removed unexpectedly, this behavior could lead to unexpected client behavior. This vulnerability is fixed in commit 123f5e2b65dcdba8f7ef659a00d24bd1249141be.

Directory traversal vulnerability in H2O before 1.4.5 and 1.5.x before 1.5.0-beta2, when the file.dir directive is enabled, allows remote attackers to read arbitrary files via a crafted URL.

CRLF injection vulnerability in the onreq function in lib/handler/redirect.c in H2O before 1.6.2 and 1.7.x before 1.7.0-beta3 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via a crafted URI.

'Mobaoku-Auction&Flea Market' App for iOS versions prior to 5.5.16 improperly verifies server certificates, which may allow an attacker to eavesdrop on an encrypted communication via a man-in-the-middle attack.