CVE-2025-55753: Apache HTTP Server

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

An integer overflow in the case of failed ACME certificate renewal leads, after a number of failures (~30 days in default configurations), to the backoff timer becoming 0. Attempts to renew the certificate then are repeated without delays until it succeeds. This issue affects Apache HTTP Server: from 2.4.30 before 2.4.66. Users are recommended to upgrade to version 2.4.66, which fixes the issue.

Affected products

• Apache HTTP Server: from 2.4.30, before 2.4.66 (fixed in 2.4.66)

Published 2025-12-05. Last modified 2026-06-17.