CVE-2018-17256: Persistent cross-site scripting (XSS) vulnerability in Umbraco CMS 7.12.3 allows authenticated users to inject

Routine

MEDIUM 4.8DOWNGRADE

CVE-2018-17256 is a medium-severity flaw (CVSS 4.8) affecting umbraco cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Persistent cross-site scripting (XSS) vulnerability in Umbraco CMS 7.12.3 allows authenticated users to inject arbitrary web script via the Header Name of a content (Blog, Content Page, etc.). The vulnerability is exploited when updating or removing public access of a content.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	4.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.7% (top 49%)
CISA exploited list	No
Weakness	CWE-79
Published	2018-11-27
Last modified	2026-06-17

Publisher (CNA): CyberSecurity Philippines - CERT · Vendor: umbraco

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

Am I affected?

Timeline

2018-11-27 19:29 UTCPublished CVE record published
2026-06-17 01:45 UTCUpdated Record last modified

umbraco umbraco cms DOWNGRADE

Affected: 7.12.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.12.3

1. Check installed version

apt-cache policy umbraco-cms || rpm -q umbraco-cms || umbraco-cms --version

2. No fixed release: DOWNGRADE to a release before 7.12.3 (Debian / Ubuntu)

apt-cache madison umbraco-cms sudo apt install umbraco-cms=<VERSION_BEFORE_7.12.3> sudo apt-mark hold umbraco-cms

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list umbraco-cms sudo dnf downgrade umbraco-cms-<VERSION_BEFORE_7.12.3> sudo dnf versionlock add umbraco-cms

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2018-17256?

umbraco cms: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-17256 being exploited?

CVE-2018-17256 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-2018-17256 affect?

CVE-2018-17256 affects umbraco cms. Severity is medium (CVSS 4.8). Persistent cross-site scripting (XSS) vulnerability in Umbraco CMS 7.12.3 allows authenticated users to inject arbitrary web script via the Header Name of a content (Blog, Content Page, etc.). The vulnerability is exploited when updating or

How urgent is CVE-2018-17256?

Priority 30/100. No elevated risk signals yet.

Related CVEs

CVE-2026-46616 MEDIUM 5.4 UPGRADE Umbraco is an ASP.NET CMS
CVE-2026-46609 MEDIUM 4.6 UPGRADE Umbraco is an ASP.NET CMS
CVE-2025-66625 MEDIUM 4.9 UPGRADE Umbraco is an ASP.NET CMS
CVE-2021-47776 MEDIUM 5.3 DOWNGRADE Umbraco CMS v8.14.1 contains a server-side request forgery vulnerability that allows attackers to manipulate b
CVE-2025-67288 CRITICAL 10.0 DOWNGRADE An arbitrary file upload vulnerability in Umbraco CMS v16.3.3 allows attackers to execute arbitrary code by up

References

← Back to latest CVEs