# CVE-2018-12542: Eclipse Vert.x does not properly neutralize '' (forward slashes) sequences that can resolve to an external location

> Attackers can read files outside the restricted directory on Windows systems using the StaticHandler in Eclipse Vert.x.

- **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:** 10 Oct 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-h39x-m55c-v55h

## What is CVE-2018-12542?

CVE-2018-12542 is a critical path traversal vulnerability in The Eclipse Foundation Eclipse Vert.x, published on 10 Oct 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In version from 3.0.0 to 3.5.3 of Eclipse Vert.x, the StaticHandler uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '\' (forward slashes) sequences that can resolve to a location that is outside of that directory when running on Windows Operating Systems.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2018-12542?

2 open source packages ship an affected version, including io.vertx:vertx-web. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.vertx:vertx-web` | Maven | From 3.0.0 | 3.5.4 |
| `io.vertx:vertx-web` | Maven | From 3.0.0 | 3.5.4 |

Products: Eclipse Vert.x.

## How do I fix CVE-2018-12542?

Upgrade io.vertx:vertx-web to 3.5.4 or later.

## Is CVE-2018-12542 being exploited?

There is no known exploitation of CVE-2018-12542 in the wild and no public exploit code.

Public exploit code:

- https://github.com/shoucheng3/vert-x3__vertx-web_CVE-2018-12542_3-5-3-CR1 (github_poc): https://github.com/shoucheng3/vert-x3__vertx-web_CVE-2018-12542_3-5-3-CR1

## Other vulnerabilities in The Eclipse Foundation Eclipse Vert.x

- [CVE-2019-17640](https://insights.sbomify.com/CVE-2019-17640/): Path Traversal in Eclipse Vert (critical 9.8)
- [CVE-2018-12544](https://insights.sbomify.com/CVE-2018-12544/): Moderate severity vulnerability that affects io.vertx:vertx-core (critical 9.8)
- [CVE-2026-102469](https://insights.sbomify.com/CVE-2026-102469/): Deserialization in Eclipse Vert.x (critical 9.2)
- [CVE-2018-12540](https://insights.sbomify.com/CVE-2018-12540/): High severity vulnerability that affects io.vertx:vertx-web (high 8.8)
- [CVE-2026-102461](https://insights.sbomify.com/CVE-2026-102461/): Denial of service in Eclipse Vert.x (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-12542 and fix it if it is affected.

What it is: CVE-2018-12542 is a critical path traversal vulnerability in The Eclipse Foundation Eclipse Vert.x, published on 10 Oct 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-2018-12542 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.vertx:vertx-web (Maven): affected from 3.0.0; fixed in 3.5.4
- io.vertx:vertx-web (Maven): affected from 3.0.0; fixed in 3.5.4

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-2018-12542/ (Markdown: https://insights.sbomify.com/CVE-2018-12542/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-12542
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-12542
- OSV: https://osv.dev/vulnerability/CVE-2018-12542

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-12542/
Summaries are generated and may contain mistakes; the official description above is the record.