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HTTP ServerWeb server / proxy · Apache

CVE-2026-43951

MEDIUM · 6.5 CVSS v3.1 Published 2026-06-08
Fix available
A fix is available. Upgrade to after 2.4.67 or later.
See remediation →
74/100
Remediation priority · Elevated
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
Out-of-bounds Read vulnerability in Apache HTTP Server with mod_headers and mod_mime and multiple response languages. This issue affects Apache HTTP Server: from 2.4.0 through 2.4.67.

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 · moderate confidence

An out-of-bounds read vulnerability exists in Apache HTTP Server when mod_headers and mod_mime modules are both enabled and the server handles multiple response languages. This memory access violation could allow an attacker to read sensitive information from memory or cause a denial of service.

MitigationUpgrade to Apache HTTP Server 2.4.68 or later. If upgrading is not immediately possible, consider disabling mod_headers or mod_mime if not required, or implement WAF rules to filter malformed header/MIME requests.

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:>= 2.4.0, <= 2.4.67

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
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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. Determine Apache HTTP Server version
    Run 'httpd -v' or 'apache2 -v' to obtain the server version number
    Affected if The version is between 2.4.0 and 2.4.67 inclusive
  2. Verify mod_headers is enabled
    Run 'httpd -M' or 'apache2ctl -M' and look for 'headers_module' in the loaded modules list, or check for 'LoadModule headers_module' in the configuration files
    Affected if mod_headers is loaded and the Apache version is in the affected range
  3. Verify mod_mime is enabled
    Run 'httpd -M' or 'apache2ctl -M' and look for 'mime_module' in the loaded modules list, or check for 'LoadModule mime_module' in the configuration files
    Affected if mod_mime is loaded and the Apache version is in the affected range
  4. Inspect language-related header configurations
    Search configuration files (httpd.conf, apache2.conf, .htaccess) for directives involving 'Accept-Language', 'Content-Language', or language handling patterns, or inspect any custom headers configured with mod_headers that process language values
    Affected if Language-related header processing is configured and the Apache version is in the affected range

A user is affected if their Apache HTTP Server version falls between 2.4.0 and 2.4.67 inclusive AND both mod_headers and mod_mime modules are enabled with language-related header configurations in use.

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 a release after 2.4.67
Interim mitigation

Upgrade to Apache HTTP Server 2.4.68 or later. If upgrading is not immediately possible, consider disabling mod_headers or mod_mime if not required, or implement WAF rules to filter malformed header/MIME requests.

Recommended fix Moderate confidence

Apache HTTP Server 2.4.68 or later stable release

  1. 1. Identify the current Apache HTTP Server version using: httpd -v or apache2 -v
  2. 2. If version is between 2.4.0 and 2.4.67 inclusive, plan for upgrade
  3. 3. Review current configuration for mod_headers and mod_mime usage, especially with multi-language response setups
  4. 4. Obtain the fixed Apache HTTP Server release (version 2.4.68 or later) from httpd.apache.org or your OS package repository
  5. 5. Back up current Apache configuration and document files: cp -r /etc/apache /etc/apache.backup
  6. 6. Install the upgraded Apache HTTP Server version
  7. 7. Verify the installation: httpd -v to confirm version
  8. 8. Test Apache startup and validate configurations: apachectl configtest
Caveat Review mod_headers and mod_mime configuration changes in release notes; test thoroughly with multi-language setups before production deployment

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

Fix this in HTTP Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA3.0 h
18.0 hours of engineering $3,060
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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-2026-43951 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