Apache HTTP Server: DoS in HTTP/2 with initial windows size 0
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EPSS
EPSS 68.82 % · centile 99 (2026-10-27)
État
PUBLISHED
Publiée
Mise à jour
Attribuée par
apache
Statut NVD
Modified
Description
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.