# CVE-2018-12026: Phusion Passenger SpawningKit Contains Arbitrary Read/Write Vulnerability

> A malicious Passenger-managed application can use symlinks to read or write arbitrary files, leading to information disclosure and privilege escalation.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jun 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-7cv3-gvmc-8mq5

## What is CVE-2018-12026?

CVE-2018-12026 is a critical path traversal vulnerability in n/a, published on 17 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2018-12026?

2 open source packages ship an affected version, including passenger. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `passenger` | RubyGems | From 5.3.0 | 5.3.2 |
| `passenger` | RubyGems | From 5.3.0 | 5.3.2 |

Products: Phusion Passenger.

## How do I fix CVE-2018-12026?

Upgrade passenger to 5.3.2 or later.

## Is CVE-2018-12026 being exploited?

There is no known exploitation of CVE-2018-12026 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-12027](https://insights.sbomify.com/CVE-2018-12027/): Insecure Permissions in Phusion Passenger (high 8.8)
- [CVE-2018-12028](https://insights.sbomify.com/CVE-2018-12028/): Incorrect Access Control in Phusion Passenger (high 7.8)
- [CVE-2016-10345](https://insights.sbomify.com/CVE-2016-10345/): Phusion Passenger uses a known /tmp filename (high 7.8)
- [CVE-2012-6135](https://insights.sbomify.com/CVE-2012-6135/): RubyGems passenger gem allows remote attackers to delete files (high 7.5)
- [CVE-2025-26803](https://insights.sbomify.com/CVE-2025-26803/): Phusion Passenger denial of service (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-12026 and fix it if it is affected.

What it is: CVE-2018-12026 is a critical path traversal vulnerability in n/a, published on 17 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-12026 in the wild and no public exploit code.

Affected packages and fixed versions:
- passenger (RubyGems): affected from 5.3.0; fixed in 5.3.2
- passenger (RubyGems): affected from 5.3.0; fixed in 5.3.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-12026/ (Markdown: https://insights.sbomify.com/CVE-2018-12026/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-12026
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-12026
- OSV: https://osv.dev/vulnerability/CVE-2018-12026

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-12026/
Summaries are generated and may contain mistakes; the official description above is the record.