dbcve.org
Mac Os XOperating system · Apple

CVE-2016-4694

CRITICAL · 9.1 CVSS v3.0 Published 2016-09-25
Fix available
A fix is available. Upgrade to after 10.11.6 or later.
See remediation →
100/100
Remediation priority · Urgent
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
The Apache HTTP Server in Apple OS X before 10.12 and OS X Server before 5.2 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted CGI client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue, a related issue to CVE-2016-5387.

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

The Apache HTTP Server in Apple OS X and OS X Server passes the HTTP_PROXY environment variable from client requests to CGI applications, following RFC 3875 section 4.1.18. Attackers can send a crafted Proxy header in HTTP requests, which gets passed to CGI applications, allowing them to redirect the application's outbound HTTP traffic to an attacker-controlled proxy server (httpoxy vulnerability).

MitigationConfigure Apache to reject or unset the Proxy header before it reaches CGI applications, typically using mod_headers to set 'RequestHeader unset Proxy' or equivalent, or configure applications to ignore the HTTP_PROXY environment variable.

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
Mac Os XOperating system
Affected:<= 10.11.6
Os X ServerOperating system
Affected:<= 5.1

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
High
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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. Check the installed OS X version
    Run 'sw_vers -productVersion' in Terminal to obtain the exact version number
    Affected if The version is 10.11.6 or earlier for Mac OS X, or the system is running OS X Server 5.1 or earlier
  2. Verify Apache HTTP Server is installed and running
    Run 'ps aux | grep -i httpd' or 'apachectl -V' to check if Apache is active
    Affected if Apache is running on an affected OS version (10.11.6 or earlier for Mac OS X, 5.1 or earlier for OS X Server)
  3. Confirm CGI module is enabled in Apache
    Run 'apachectl -M 2>/dev/null | grep -i cgi' or inspect the Apache configuration files (typically in /etc/apache2/) for 'LoadModule cgi_module' or 'Options +ExecCGI' directives
    Affected if CGI support is enabled in Apache configuration
  4. Check for CGI applications that honor HTTP_PROXY
    Review the contents of /Library/WebServer/CGI-Executables/ or /Library/WebServer/Documents/ for CGI scripts, and identify any that perform outbound HTTP requests using libraries that respect the HTTP_PROXY environment variable
    Affected if CGI applications that make outbound HTTP connections are present and accessible via Apache
  5. Inspect Apache configuration for mitigation headers
    Examine Apache config files (httpd.conf, included conf files) for directives such as 'RequestHeader unset Proxy' or 'RequestHeader unset Proxy' within a <VirtualHost> or <Directory> block
    Affected if The 'RequestHeader unset Proxy' directive is NOT present in the Apache configuration, meaning the Proxy header is not being blocked before reaching CGI applications

The environment is affected if running Mac OS X 10.11.6 or earlier (or OS X Server 5.1 or earlier) with Apache and CGI enabled, and the Apache configuration lacks the 'RequestHeader unset Proxy' directive to block the Proxy header.

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 10.11.6
Interim mitigation

Configure Apache to reject or unset the Proxy header before it reaches CGI applications, typically using mod_headers to set 'RequestHeader unset Proxy' or equivalent, or configure applications to ignore the HTTP_PROXY environment variable.

Recommended fix High confidence

macOS 10.12 (Sierra) or OS X Server 5.2 and later

  1. Back up all critical data and verify backups are restorable
  2. Confirm current system version is at Mac OS X 10.11.6 or earlier, or OS X Server 5.1 or earlier
  3. Download macOS 10.12 (Sierra) or later from the Mac App Store or Apple's website, or obtain OS X Server 5.2 or later
  4. Create a bootable installer or use macOS Recovery to perform a clean installation, or upgrade in place through System Preferences > Software Update
  5. After upgrading, verify the Apache HTTP Server version includes the httpoxy fix by checking that CGI scripts no longer inherit HTTP_PROXY from Proxy headers
  6. Test that applications using CGI continue to function correctly after the upgrade
Caveat Major OS upgrade may introduce compatibility issues with older applications; review app compatibility before upgrading

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

Fix this in Mac Os X Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2016-4694 — 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-2016-4694 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