# CVE-2018-6553: AppArmor cupsd Sandbox Bypass Due to Use of Hard Links

> A local attacker can escape AppArmor confinement in CUPS via hard links, potentially escalating privileges or bypassing security restrictions.

- **Severity:** High 8.8 (`CVSS:3.0/AV:L/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Aug 2018
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2018-6553, GHSA-2f8v-v7q3-8gqv, MINI-jprg-cx62-4gvr, UBUNTU-CVE-2018-6553

## What is CVE-2018-6553?

CVE-2018-6553 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 10 Aug 2018. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The CUPS AppArmor profile incorrectly confined the dnssd backend due to use of hard links. A local attacker could possibly use this issue to escape confinement. This flaw affects versions prior to 2.2.7-1ubuntu2.1 in Ubuntu 18.04 LTS, prior to 2.2.4-7ubuntu3.1 in Ubuntu 17.10, prior to 2.1.3-4ubuntu0.5 in Ubuntu 16.04 LTS, and prior to 1.7.2-0ubuntu1.10 in Ubuntu 14.04 LTS.

## Which versions are affected by CVE-2018-6553?

It affects 3 products.


Products: Canonical Ubuntu Linux, Cups Cups, Debian Debian Linux.

## How do I fix CVE-2018-6553?

Apply the vendor's patch.

## Is CVE-2018-6553 being exploited?

There is no known exploitation of CVE-2018-6553 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-2018-6553 and fix it if it is affected.

What it is: CVE-2018-6553 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 10 Aug 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-2018-6553 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-2018-6553/ (Markdown: https://insights.sbomify.com/CVE-2018-6553/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-6553
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-6553
- OSV: https://osv.dev/vulnerability/CVE-2018-6553

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-6553/
Summaries are generated and may contain mistakes; the official description above is the record.