CVE-2026-111624
Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubs
- State
- Published
- Severity
- 6.3 Medium
- Published
- Oct 16, 2026
- Updated
- Oct 21, 2026
- Reserved
- Oct 16, 2026
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can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.3 Medium | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 3.7 Low | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | VulnCheck |
Weaknesses
- CWE-306 Missing Authentication for Critical Function
Affected Products
| Product | Versions |
|---|---|
Umbraco-CMSumbraco |
|
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-L11technical-description
- https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Management/Preview/PreviewHubUpdater.cs#L58technical-description
- https://github.com/umbraco/Umbraco-CMS/commit/b4f6cfc9d0955f9d8443e68353db4a692e91bd94patch
- https://github.com/umbraco/Umbraco-CMS/commit/243e082479c777d0f585bbd2f8db571607767b22patch
- Umbraco-CMS release-18.2.1 Release Notesrelease-notes
- Umbraco-CMS release-17.7.1 Release Notesrelease-notes
- VulnCheck Advisory: Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubsthird-party-advisory
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