dbcve.org
HTTP ServerWeb server / proxy · Apache

CVE-2006-20001

HIGH · 7.5 CVSS v3.1 Published 2023-01-17
Fix available
A fix is available. Upgrade to 2.4.55 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
A carefully crafted If: request header can cause a memory read, or write of a single zero byte, in a pool (heap) memory location beyond the header value sent. This could cause the process to crash. This issue affects Apache HTTP Server 2.4.54 and earlier.

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

This vulnerability in Apache HTTP Server 2.4.54 and earlier involves heap memory corruption via a specially crafted If: request header. The header parsing logic allows reading or writing a single zero byte to a pool (heap) memory location beyond the allocated header value buffer, potentially causing the Apache process to crash.

MitigationUpgrade Apache HTTP Server to version 2.4.55 or later to obtain the security patch. Organizations unable to immediately upgrade should consider deploying a WAF rule to filter or block malformed If: headers, or implement rate limiting on requests containing this header.

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:< 2.4.55

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
None
Integrity
None
Availability
High

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

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. Determine Apache HTTP Server version
    Run `httpd -v` or `apache2 -v` from the command line, or check the server response header `Server:` for the Apache version string
    Affected if The installed version is less than 2.4.55 (for example, 2.4.54, 2.4.53, 2.4.52, etc.)
  2. Confirm Apache is the web server in use
    Check the HTTP response header `Server:` field returned by your web server, or review the server software listed in your running services
    Affected if The server identifies itself as Apache with a version below 2.4.55
  3. Verify the Apache package name
    On Linux, run `dpkg -l | grep apache` or `rpm -qa | grep httpd` to list installed Apache packages; on Windows, check installed programs for Apache HTTP Server
    Affected if The installed Apache package version is below 2.4.55

You are affected if your Apache HTTP Server installation shows a version number lower than 2.4.55, as the heap corruption flaw in If: header parsing exists in all earlier versions.

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 2.4.55 or later
Fixed in 2.4.55
Interim mitigation

Upgrade Apache HTTP Server to version 2.4.55 or later to obtain the security patch. Organizations unable to immediately upgrade should consider deploying a WAF rule to filter or block malformed If: headers, or implement rate limiting on requests containing this header.

Recommended fix High confidence

Apache HTTP Server 2.4.55

  1. 1. Check current Apache HTTP Server version by running 'httpd -v' or 'apache2 -v'
  2. 2. If version is below 2.4.55, plan for upgrade during a maintenance window
  3. 3. Download Apache HTTP Server 2.4.55 or later from httpd.apache.org or use your system's package manager
  4. 4. Stop the Apache HTTP Server service (e.g., 'systemctl stop httpd' or 'apachectl stop')
  5. 5. Backup your current Apache configuration andhtdocs directories
  6. 6. Install the new version using your package manager or compile from source
  7. 7. Restore your configuration files if needed
  8. 8. Start the Apache HTTP Server service (e.g., 'systemctl start httpd' or 'apachectl start')
Caveat Upgrading within the 2.4.x branch typically has minimal breaking changes; however, review the release notes for any configuration or module changes before upgrading in production environments.

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

Fix this in HTTP Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.

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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-2006-20001 in production — separate from our analysis above.

No notes yet

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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