CVE-2018-12027
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 · uneditedAn Insecure Permissions vulnerability in SpawningKit in Phusion Passenger 5.3.x before 5.3.2 causes information disclosure in the following situation: given a Passenger-spawned application process that reports that it listens on a certain Unix domain socket, if any of the parent directories of said socket are writable by a normal user that is not the application's user, then that non-application user can swap that directory with something else, resulting in traffic being redirected to a non-application user's process through an alternative Unix domain socket.
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 confidenceSpawningKit in Phusion Passenger 5.3.x before 5.3.2 has an insecure permissions vulnerability where Unix domain socket parent directories writable by non-application users allow a local attacker to perform a directory swap attack, redirecting application traffic to their own process through an alternative socket.
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>= 5.3.0, < 5.3.2CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/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 checksWork through these to decide whether this CVE applies to you.
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Verify Phusion Passenger is installedRun `passenger --version` or check for Passenger binaries in /usr/bin, /opt, or other common installation directoriesAffected if Passenger is installed and the version is 5.3.0, 5.3.1, or any 5.3.x version below 5.3.2
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Confirm the installed version numberCompare the version output from `passenger --version` against the affected range >= 5.3.0 and < 5.3.2Affected if The version falls within 5.3.0 through 5.3.1 inclusive
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Identify Passenger socket directoriesInspect Passenger configuration files (typically in /etc/passenger or within the application directory) to locate the Unix domain socket directories used by SpawningKitAffected if Socket parent directories exist and are writable by non-root users outside the application user group
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Check directory permissions on socket pathsUse `ls -la` on the identified socket parent directories and verify write permissions for non-application users (typically other: or group: permissions include 'w')Affected if Any non-application user has write access (o+w or g+w) to directories containing Passenger Unix sockets
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Verify socket file ownership and permissionsRun `ls -la` on the actual socket files created by Passenger and check if the socket parent directory could be replaced by an attackerAffected if Socket parent directories allow directory replacement or symlink attacks due to weak permissions
A system is affected if Phusion Passenger version 5.3.0-5.3.1 is running and Unix domain socket parent directories are writable by non-application users, allowing a local attacker to perform a directory swap attack.
Generated from the published advisory. Verify against your own configuration.
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 data5.3.2
Upgrade Phusion Passenger to version 5.3.2 or later which includes fixed permission validation in SpawningKit to prevent socket directory manipulation.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12027 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-12027 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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