CVE-2023-43622: Apache HTTP Server

High severity, CVSS 7.5. EPSS: 70.6% chance of exploitation in the next 30 days.

An attacker, opening a HTTP/2 connection with an initial window size of 0, was able to block handling of that connection indefinitely in Apache HTTP Server. This could be used to exhaust worker resources in the server, similar to the well known "slow loris" attack pattern. This has been fixed in version 2.4.58, so that such connection are terminated properly after the configured connection timeout. This issue affects Apache HTTP Server: from 2.4.55 through 2.4.57. Users are recommended to upgrade to version 2.4.58, which fixes the issue.

Affected products

• Apache HTTP Server: from 2.4.55, before 2.4.58 (fixed in 2.4.58)

Published 2023-10-23. Last modified 2026-06-17.