Auth bypass in Umbraco Umbraco-Cms
CVE-2026-111624
Umbraco CMS before 17.7.1 and 18.2.1 contains a missing authorization vulnerability that allows unauthenticated clients to connect to the backoffice PreviewHub and BackofficeHub SignalR hubs. Attackers can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-4c5q-6c64-96j7 (vendor-advisory)
- github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Manageme… (technical-description)
- github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Manageme… (technical-description)
- github.com/umbraco/Umbraco-CMS/commit/b4f6cfc9d0955f9d8443e68353db4a692e91bd94 (patch)
- github.com/umbraco/Umbraco-CMS/commit/243e082479c777d0f585bbd2f8db571607767b22 (patch)
- github.com/umbraco/Umbraco-CMS/releases/tag/release-18.2.1 (release-notes)
- github.com/umbraco/Umbraco-CMS/releases/tag/release-17.7.1 (release-notes)
- www.vulncheck.com/advisories/umbraco-cms-before-17.7.1-and-18.2.1-missing-autho… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-111624?
- CVE-2026-111624 is a low-severity vulnerability in Umbraco Umbraco-Cms, classified under Missing Authentication for Critical Function. CVSS score: 3.7/10. Published 2026-10-16.
- How severe is CVE-2026-111624?
- Low severity. CVSS v3 base score is 3.7 out of 10.