# CVE-2018-6954: Path traversal in n/a

> Local attackers can gain ownership of arbitrary files by exploiting symlink handling in systemd-tmpfiles, bypassing protected symlink settings.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Feb 2018
- **Updated:** 9 Jun 2025
- **Also known as:** DEBIAN-CVE-2018-6954, GHSA-fgm4-rh7c-g9fg, UBUNTU-CVE-2018-6954, USN-3816-2

## What is CVE-2018-6954?

CVE-2018-6954 is a high-severity path traversal vulnerability in Canonical Ubuntu Linux, published on 13 Feb 2018. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

systemd-tmpfiles in systemd through 237 mishandles symlinks present in non-terminal path components, which allows local users to obtain ownership of arbitrary files via vectors involving creation of a directory and a file under that directory, and later replacing that directory with a symlink. This occurs even if the fs.protected_symlinks sysctl is turned on.

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

## Which versions are affected by CVE-2018-6954?

It affects 3 products.


Products: Canonical Ubuntu Linux, Opensuse Leap, Systemd Project Systemd.

## How do I fix CVE-2018-6954?

Apply the vendor's patch.

## Is CVE-2018-6954 being exploited?

There is no known exploitation of CVE-2018-6954 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-6954 and fix it if it is affected.

What it is: CVE-2018-6954 is a high-severity path traversal vulnerability in Canonical Ubuntu Linux, published on 13 Feb 2018. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-6954 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. 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-2018-6954/ (Markdown: https://insights.sbomify.com/CVE-2018-6954/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-6954
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-6954
- OSV: https://osv.dev/vulnerability/CVE-2018-6954

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-6954/
Summaries are generated and may contain mistakes; the official description above is the record.