CVE-2023-44487
Description
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
Security Bulletin
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | 7.5 | 7.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
