CVE-2018-6553: The CUPS AppArmor profile incorrectly confined the dnssd backend due to use of hard links

This month

HIGH 8.8WATCHLISTMITIGATEMITIGATEMITIGATE

CVE-2018-6553 is a high-severity flaw (CVSS 8.8) affecting cups, ubuntu linux, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Published	2018-08-10
Last modified	2026-06-17

Publisher (CNA): Canonical Ltd. · Vendor: canonical · cups · debian

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-08-10 15:29 UTCPublished CVE record published
2026-06-17 02:02 UTCUpdated Record last modified

cups cups MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cups || rpm -q cups || cups --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

canonical ubuntu linux MITIGATE

Affected: 14.04 · 16.04 · 17.10 · 18.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 14.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-6553?

cups: mitigate or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-6553 being exploited?

CVE-2018-6553 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-6553 affect?

CVE-2018-6553 affects cups, ubuntu linux, debian linux. Severity is high (CVSS 8.8). 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

How urgent is CVE-2018-6553?

Priority 44/100. High severity; On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities

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References

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