A flaw was found in libxml2's xmlBuildQName function, where integer overflows in buffer size calculations can lead to a stack-based buffer overflow. This issue can result in memory corruption or a denial of service when processing crafted input.

A flaw was found in libxml2. This vulnerability occurs when the library processes a specially crafted XML Schema Definition (XSD) validated document that includes an internal entity reference. An attacker could exploit this by providing a malicious document, leading to a type confusion error that causes the application to crash. This results in a denial of service (DoS), making the affected system or application unavailable.

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.

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 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.

A NULL pointer dereference flaw was found in libxml2, where it did not propagate errors while parsing XML mixed content. This flaw causes the application to crash if an untrusted XML document is parsed in recovery mode and post validated. The highest threat from this vulnerability is to system availability.

An use-after-free was found in xmllint when used with --html and --push options when processing crafted files.

Reference: https://gitlab.gnome.org/GNOME/libxml2/-/issues/230

Upstream patch: https://gitlab.gnome.org/GNOME/libxml2/-/commit/1358d157d0bd83be1dfe356a69213df9fac0b539

A heap-based buffer overflow was found in libxml2 when processing truncated UTF-8 input.

Reference: https://gitlab.gnome.org/GNOME/libxml2/-/issues/235

Upstream patch: https://gitlab.gnome.org/GNOME/libxml2/-/commit/bf22713507fe1fc3a2c4b525cf0a88c2dc87a3a2

ActionKit. An input validation issue was addressed with improved input validation.

Apache HTTP Server, with MPM event, worker or prefork, code executing in less-privileged child processes or threads (including scripts executed by an in-process scripting interpreter) could execute code with the privileges of the parent process (usually root) by manipulating the scoreboard.

A flaw was found in HTTP/2. Using frames with an empty payload, a flood could occur that results in excessive CPU usage and starvation of other clients. The highest threat from this vulnerability is to system availability.

Apache httpd before version 2.4.34 has a vulnerability in the handling of specially crafted HTTP/2 requests, causing workers to be allocated 60 seconds longer than necessary, leading to worker exhaustion and a denial of service.

This issue only affects servers that have configured and enabled HTTP/2 support, which is not the default

External References:

https://httpd.apache.org/security/vulnerabilities24.html#CVE-2018-1333

APR. Multiple issues in Perl were addressed with improved memory handling.

Apache HTTP Server, in all releases prior to 2.2.32 and 2.4.25, was liberal in the whitespace accepted from requests and sent in response lines and headers. Accepting these different behaviors represented a security concern when httpd participates in any chain of proxies or interacts with back-end application servers, either through modproxy or using conventional CGI mechanisms, and may result in request smuggling, response splitting and cache pollution.

apache. Multiple issues existed in Apache. These were addressed by updating Apache to version 2.4.25.

A flaw was found in HTTP/2. Using HEADER frames with invalid HTTP headers and queuing of response RSTSTREAM frames, an attacker could cause a flood resulting in unbounded memory growth. The highest threat from this vulnerability is to system availability.

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.