Resource Exhaustion Affecting mod_http2 package, versions <0:2.0.26-1.el9


Severity

Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
70.6% (100th percentile)

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  • Snyk IDSNYK-RHEL9-MODHTTP2-12608581
  • published10 Sept 2025
  • disclosed10 Oct 2023

Introduced: 10 Oct 2023

CVE-2023-43622  (opens in a new tab)
CWE-400  (opens in a new tab)

How to fix?

Upgrade RHEL:9 mod_http2 to version 0:2.0.26-1.el9 or higher.
This issue was patched in RHSA-2024:2368.

NVD Description

Note: Versions mentioned in the description apply only to the upstream mod_http2 package and not the mod_http2 package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1