CVE-2018-12026
CRITICALCVE-2018-12026 is a critical-severity (CVSS 9.8) CWE-59 vulnerability in passenger. O3 Security confirms whether CVE-2018-12026 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Phusion Passenger SpawningKit Contains Arbitrary Read/Write Vulnerability
Blast Radius
passengerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
During 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | passenger | ≥ 5.3.0&&< 5.3.2 | 5.3.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for passenger. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update passenger to 5.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-12026 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2018-12026 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2018-12026. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2018-12026 in your dependencies?
O3 detects CVE-2018-12026 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.