Understanding the Impact of CVE-2023-43622 on the Apache HTTP Server

The recent discovery of CVE-2023-43622 in Apache HTTP Server has raised concerns about server security and resource management. With a severity rating of HIGH and a score of 7.5, this vulnerability poses a significant risk to systems running outdated versions of Apache HTTP Server, specifically from versions 2.4.55 to 2.4.57.

What is Apache HTTP Server?

Apache HTTP Server is one of the most popular web server software systems worldwide. It is an open-source software that supports various operating systems including Unix, FreeBSD, Solaris, and Microsoft Windows. Apache facilitates the delivery of content over the internet by hosting one or more websites. Given its wide usage, vulnerabilities within Apache HTTP Server can have extensive implications for numerous organizations and networks.

Details of the Vulnerability:

Identified as CVE-2023-43622, the vulnerability specifically stems from a misuse of the HTTP/2 initial window size setting. An attacker can exploit this by opening a connection with a window size of zero, which unexpectedly halts the management of this connection, causing an indefinite block. This blockage can subsequently exhaust the server’s resources. This method of attack resembles the notorious "slow loris" technique where limited resources of a target server are tied up by holding connections open for as long as possible.

Security Implications:

This vulnerability is crucial as it directly affects the server's availability, potentially leading to service degradation or total denial of service (DOS). The impact is thus not merely confined to a decrease in performance but escalates to a complete compromise in resource availability, underscoring the urgency for corrective measures.

Remedial Action:

The Apache team has addressed this issue promptly with a fix included in Apache HTTP Server version 2.4.58. It is crucial for users operating versions 2.4.55 through 2.4.57 to upgrade to this latest version immediately to mitigate the risks posed by CVE-2023-43622. The update ensures that connections with an initial window size of zero are correctly terminated after the configured connection timeout, thus restoring the resilience and stability of the server operations.


Users are urged to prioritize this update to prevent potential exploits that could target this vulnerability. Regular updates and vigilant monitoring of network systems are also recommended as best practices in maintaining robust security protocols.

Need Assistance with Secure Patch Management?

Keeping up-to-date with the latest security patches is essential but can be challenging. LinuxPatch.com offers a comprehensive patch management platform tailored for Linux servers, designed to simplify and secure your patching process efficiently. With LinuxPatch.com, ensure your systems are protected against vulnerabilities like CVE-2023-43622 without the hassle of manual updates.


The discovery of CVE-2023-43622 highlights the critical nature of maintaining server software in its most secure, updated form. By taking swift action to upgrade to Apache HTTP Server 2.4.58, organizations can safeguard their systems from potential threats that exploit vulnerabilities. Remember, in the dynamic realm of cybersecurity, being proactive is not just an option—it is a necessity.