dbcve.org
HTTP ServerWeb server / proxy · Apache

CVE-2025-55753

HIGH · 7.5 CVSS v3.1 Published 2025-12-05
Fix available
A fix is available. Upgrade to 2.4.66 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Apache HTTP Server versions 2.4.30 through 2.4.65 contain an integer overflow in the ACME certificate renewal logic. After approximately 30 days of renewal failures, the backoff timer wraps to 0, causing unlimited retry attempts without any delay between certificate renewal requests.

MitigationUpgrade Apache HTTP Server to version 2.4.66 or later to remediate this vulnerability. Monitor certificate renewal logs for repeated failure patterns in older versions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
HTTP ServerWeb server / proxy
Affected:>= 2.4.30, < 2.4.66

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Apache HTTP Server version
    Run 'httpd -v' or 'apache2 -v' to obtain the installed server version
    Affected if Installed version is 2.4.30 through 2.4.65 inclusive
  2. Confirm ACME certificate renewal is in use
    Inspect server configuration for mod_md (mod_ssl with ACME provider) or Let's Encrypt certificate renewal directives
    Affected if Server is configured to automatically renew SSL certificates via ACME protocol
  3. Examine certificate renewal logs
    Review error logs (error.log) for ACME renewal failures, focusing on timestamps and frequency of renewal attempts over a 30+ day period
    Affected if Logs show continuous renewal failure patterns without the expected exponential backoff delay between attempts

User is affected if running Apache 2.4.30-2.4.65 with ACME-based certificate renewal enabled, and logs reveal renewal failures occurring over approximately 30 days resulting in rapid retry loops without delay.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.4.66 or later
Fixed in 2.4.66
Interim mitigation

Upgrade Apache HTTP Server to version 2.4.66 or later to remediate this vulnerability. Monitor certificate renewal logs for repeated failure patterns in older versions.

Recommended fix High confidence

2.4.66

  1. 1. Back up your current Apache HTTP Server configuration and data directories (typically /etc/httpd or /etc/apache2)
  2. 2. Stop the Apache HTTP Server service (e.g., systemctl stop httpd or systemctl stop apache2)
  3. 3. Obtain Apache HTTP Server version 2.4.66 from your distribution's package repository or the official Apache HTTP Server download page at httpd.apache.org
  4. 4. Install the upgrade using your system's package manager (e.g., yum update httpd, apt-get install apache2, or similar)
  5. 5. Verify the installed version matches 2.4.66 using 'httpd -v' or 'apache2 -v'
  6. 6. Review and restore any custom configuration files if needed
  7. 7. Start the Apache HTTP Server service (e.g., systemctl start httpd or systemctl start apache2)
  8. 8. Verify the server is running correctly and check logs for any errors
Caveat Review the Apache HTTP Server 2.4.66 release notes for any configuration or module changes compared to your current version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in HTTP Server Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-55753 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-55753 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data