dbcve.org
Debian LinuxOperating system · Debian

CVE-2018-12029

HIGH · 7.0 CVSS v3.0 Published 2018-06-17
Fix available
A fix is available. Upgrade to 5.3.2 or later.
See remediation →
72/100
Remediation priority · Elevated
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 race condition in the nginx module in Phusion Passenger 3.x through 5.x before 5.3.2 allows local escalation of privileges when a non-standard passenger_instance_registry_dir with insufficiently strict permissions is configured. Replacing a file with a symlink after the file was created, but before it was chowned, leads to the target of the link being chowned via the path. Targeting sensitive files such as root's crontab file allows privilege escalation.

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

A race condition in Phusion Passenger's nginx module (versions 3.x through 5.x before 5.3.2) allows local privilege escalation when passenger_instance_registry_dir is configured with insufficiently strict permissions. An attacker can exploit a time window between file creation and chown operations by replacing a file with a symlink, causing the chown to operate on the symlink target instead (TOCTOU race). This enables targeting sensitive files such as root's crontab for privilege escalation.

MitigationUpgrade to Phusion Passenger 5.3.2 or later, and ensure passenger_instance_registry_dir is set to restrictive permissions (700) owned by the Passenger-running user to prevent symlink manipulation.

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
Debian LinuxOperating system
Affected:= 8.0
PassengerApplication
Affected:>= 3.0.0, < 5.3.2

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
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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. Identify installed Phusion Passenger version
    Run 'passenger --version' or check the passenger gem/package version to determine if it is less than 5.3.2
    Affected if Version is 3.x through 5.x but below 5.3.2
  2. Verify nginx module is in use
    Check nginx configuration files (typically in /etc/nginx/) for 'passenger_module' or 'load_module' directives pointing to passenger
    Affected if nginx is configured to load the Phusion Passenger module and the passenger version is vulnerable
  3. Locate passenger_instance_registry_dir setting
    Check nginx configuration or passenger configuration files for the 'passenger_instance_registry_dir' directive
    Affected if This directive is explicitly configured or defaults to a world-accessible location
  4. Inspect directory permissions on passenger_instance_registry_dir
    Use 'ls -la' on the identified passenger_instance_registry_dir path to view owner and permissions
    Affected if Permissions are not restrictive (not 700) or ownership is not set to the Passenger-running user, allowing other users to manipulate files
  5. Check for symlinks within passenger_instance_registry_dir
    List contents of the directory and look for symlinks using 'ls -la' with attention to symlink indicators
    Affected if Symlinks exist within this directory, indicating potential exploitation attempt or weak permissions enabling symlink creation

The environment is affected if Phusion Passenger versions 3.0.0 to below 5.3.2 is running with nginx, and the passenger_instance_registry_dir has permissions stricter than 700 or is owned by a different user than the Passenger process user.

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.

From vendor data
Upgrade available Upgrade to 5.3.2 or later
Fixed in 5.3.2
Interim mitigation

Upgrade to Phusion Passenger 5.3.2 or later, and ensure passenger_instance_registry_dir is set to restrictive permissions (700) owned by the Passenger-running user to prevent symlink manipulation.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2018-12029 — 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-2018-12029 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