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Understanding Recent Security Updates in Apache HTTP Server 2.4

December 19, 2023

The Apache HTTP Server 2.4 has recently undergone significant security updates to address various vulnerabilities. This article will discuss these updates, focusing on the most critical vulnerabilities and their implications for server security.

Recent Security Fixes in Apache HTTP Server 2.4

  1. mod_macro Buffer Over-Read (CVE-2023-31122): A low-impact vulnerability in the mod_macro module of Apache HTTP Server 2.4.57 and earlier versions was identified. This out-of-bounds read vulnerability could potentially allow unauthorized access to server memory. It was fixed in the 2.4.58 release​​.
  2. DoS in HTTP/2 (CVE-2023-43622): A low-impact denial-of-service (DoS) vulnerability was discovered in Apache HTTP Server versions 2.4.55 to 2.4.57. Attackers could open an HTTP/2 connection with an initial window size of 0, indefinitely blocking connection handling and potentially exhausting server resources. The issue has been resolved in version 2.4.58​​.
  3. HTTP/2 Stream Memory Issue (CVE-2023-45802): A moderate-impact vulnerability was found where memory resources for HTTP/2 streams were not immediately reclaimed upon a reset by a client. This could lead to a growing memory footprint, potentially causing the server to run out of memory. This issue affects versions up to 2.4.57 and was fixed in version 2.4.58​​.
  4. HTTP Request Splitting with mod_rewrite and mod_proxy (CVE-2023-25690): An important vulnerability was identified in some configurations of mod_proxy on Apache HTTP Server versions 2.4.0 through 2.4.55, allowing HTTP Request Smuggling attacks. The issue was resolved in the 2.4.56 update​​.
  5. mod_proxy_uwsgi HTTP Response Splitting (CVE-2023-27522): A moderate-impact vulnerability in Apache HTTP Server versions 2.4.30 through 2.4.55 was discovered, where special characters in origin response headers could lead to HTTP response smuggling. This issue was also fixed in version 2.4.56​​.

Implications and Recommendations

These vulnerabilities highlight the continuous need for vigilance in server security management. Administrators of Apache HTTP Server 2.4 should promptly update to the latest versions to mitigate these security risks. Regularly monitoring and updating server software is crucial for maintaining a secure and efficient web server environment.


The recent updates to Apache HTTP Server 2.4 demonstrate Apache’s commitment to security and efficiency. Understanding and applying these updates is essential for administrators to ensure the integrity and reliability of their server infrastructure.