# CVE-2018-18556: Privilege escalation in n/a

> A malicious operator user can exploit improper input validation in the pppd binary to execute arbitrary commands with root privileges.

- **Severity:** Critical 9.9 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Dec 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-8jmm-6g59-87gc

## What is CVE-2018-18556?

CVE-2018-18556 is a critical vulnerability in n/a, published on 17 Dec 2018. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious operator user can run the binary with elevated permissions and leverage its improper input validation condition to spawn an attacker-controlled shell with root privileges.

## Which versions are affected by CVE-2018-18556?

It affects 1 product.


Products: Vyos Vyos.

## How do I fix CVE-2018-18556?

No fix has been published for CVE-2018-18556 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-18556 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-18556 exists.

Public exploit code:

- VyOS restricted-shell Escape and Privilege Escalation (metasploit)

## Other vulnerabilities in n/a

- [CVE-2018-18555](https://insights.sbomify.com/CVE-2018-18555/): Command injection in n/a (critical 9.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-18556 and fix it if it is affected.

What it is: CVE-2018-18556 is a critical vulnerability in n/a, published on 17 Dec 2018. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-18556 exists.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2018-18556/ (Markdown: https://insights.sbomify.com/CVE-2018-18556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-18556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-18556
- OSV: https://osv.dev/vulnerability/CVE-2018-18556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-18556/
Summaries are generated and may contain mistakes; the official description above is the record.