CVE-2018-12026
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 · uneditedDuring the spawning of a malicious Passenger-managed application, SpawningKit in Phusion Passenger 5.3.x before 5.3.2 allows such applications to replace key files or directories in the spawning communication directory with symlinks. This then could result in arbitrary reads and writes, which in turn can result in information disclosure and 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 confidenceSpawningKit in Phusion Passenger 5.3.x before 5.3.2 contains a race condition where malicious applications can replace files or directories in the spawning communication directory with symlinks during the spawn process. This allows the application to manipulate the spawning mechanism to achieve arbitrary file reads and writes, leading to information disclosure and potential privilege escalation.
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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/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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Check installed Phusion Passenger versionRun 'passenger --version' or 'passenger-config --version' to get the installed version numberAffected if The version is 5.3.0 or 5.3.1 (falls within >= 5.3.0, < 5.3.2)
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Identify the spawner type in useRun 'passenger-config --spawner-type' or inspect the Passenger configuration to see if SpawningKit is enabled as the spawnerAffected if SpawningKit (the spawner type 'smart' or 'smart-lv' in older configs) is in use; this is the default spawner in affected versions
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Locate the spawning communication directoryRun 'passenger-config --root' to find the Passenger installation, then check the 'tmp' or 'var' subdirectories for the spawner working directory; the exact path varies by installationAffected if The spawning directory exists and is writable by the application user (allows symlink placement during spawn)
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Verify directory permissions on the spawn directoryInspect permissions on the spawn directory found in the previous step using 'ls -la' - look for world-writable or group-writable settingsAffected if The directory has permissive permissions (such as 777 or group-writable) that allow other users to create symlinks in it
A system is affected if it runs Phusion Passenger version 5.3.0 or 5.3.1 with SpawningKit as the spawner and has a writable spawning communication directory where symlink race conditions could occur.
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.
dbcve · scoped5.3.2
Upgrade Phusion Passenger to version 5.3.2 or later to address the symlink vulnerability in SpawningKit.
Passenger 5.3.2 or later (preferably latest stable 5.x release)
- 1. Identify current Passenger version using `passenger --version` or check your installed package version
- 2. Upgrade Passenger to version 5.3.2 or later. For example: `gem install passenger` (if using gem), or use your system's package manager to install the updated package
- 3. Restart Passenger and the web server (Apache or Nginx) to ensure the updated version is loaded
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12026 — 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-2018-12026 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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- 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
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