CVE-2023-44487

A flaw was found in handling multiplexed streams in the HTTP/2 protocol. A client can repeatedly make a request for a new multiplex stream and immediately send an RST_STREAM frame to cancel it. This creates extra work for the server setting up and tearing down the streams while not hitting any server-side limit for the maximum number of active streams per connection, resulting in a denial of service due to server resource consumption. Red Hat has rated the severity of this flaw as 'Important' as the US Cybersecurity and Infrastructure Security Agency (CISA) declared this vulnerability an active exploit.

CVE-2023-39325 was assigned for the Rapid Reset Attack in the Go language packages.

Security Bulletin https://access.redhat.com/security/vulnerabilities/RHSB-2023-003

NGINX has been marked as Moderate Impact because, for performance and resource consumption reasons, NGINX limits the number of concurrent streams to a default of 128. In addition, to optimally balance network and server performance, NGINX allows the client to persist HTTP connections for up to 1000 requests by default using an HTTP keepalive.

The majority of RHEL utilities are not long-running applications; instead, they are command-line tools. These tools utilize Golang package as build-time dependency, which is why they are classified as having a "Moderate" level of impact.

rhc component is no longer impacted by CVE-2023-44487 & CVE-2023-39325.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Users are strongly urged to update their software as soon as fixes are available. There are several mitigation approaches for this flaw.

1. If circumstances permit, users may disable http2 endpoints to circumvent the flaw altogether until a fix is available.
2. IP-based blocking or flood protection and rate control tools may be used at network endpoints to filter incoming traffic.
3. Several package specific mitigations are also available. a. nginx: https://www.nginx.com/blog/http-2-rapid-reset-attack-impacting-f5-nginx-products/ b. netty: https://github.com/netty/netty/security/advisories/GHSA-xpw8-rcwv-8f8p c. haproxy: https://www.haproxy.com/blog/haproxy-is-not-affected-by-the-http-2-rapid-reset-attack-cve-2023-44487 d. nghttp2: https://github.com/nghttp2/nghttp2/security/advisories/GHSA-vx74-f528-fxqg e. golang: The default stream concurrency limit in golang is 250 streams (requests) per HTTP/2 connection. This value may be adjusted in the golang.org/x/net/http2 package using the Server.MaxConcurrentStreams setting and the ConfigureServer function which are available in golang.org/x/net/http2.