Vulnerability · Published Oct 16, 2026 · Assigned by VulnCheck
CVE-2026-111624Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubs
Low 3.7
In plain English
A low-severity missing authentication in Umbraco-CMS from umbraco. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities).
Official description
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can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| umbraco | Umbraco-CMS | 17.0.0 – before 17.7.118.0.0 – before 18.2.1 |
Weakness: CWE-306 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
References
- GitHub Security Advisory (GHSA-4c5q-6c64-96j7) vendor-advisory
- https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Management/Preview/PreviewHub.cs#L9-L11 technical-description
- https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Management/Preview/PreviewHubUpdater.cs#L58 technical-description
- https://github.com/umbraco/Umbraco-CMS/commit/b4f6cfc9d0955f9d8443e68353db4a692e91bd94 patch
- https://github.com/umbraco/Umbraco-CMS/commit/243e082479c777d0f585bbd2f8db571607767b22 patch
- Umbraco-CMS release-18.2.1 Release Notes release-notes
- Umbraco-CMS release-17.7.1 Release Notes release-notes
- VulnCheck Advisory: Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubs third-party-advisory