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can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.

Attack Vector Network

Attack Complexity High

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact None

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
umbraco Umbraco-CMS unaffected
Version Status Constraints
17.0.0 affected < 17.7.1
18.0.0 affected < 18.2.1

No data.

No data.

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Project Subscriptions

Vendors Products
Umbraco Subscribe
Umbraco Cms Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Management/Preview/PreviewHub.cs#L9-L11 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.0/src/Umbraco.Cms.Api.Management/Preview/PreviewHubUpdater.cs#L58 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/commit/243e082479c777d0f585bbd2f8db571607767b22 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/commit/b4f6cfc9d0955f9d8443e68353db4a692e91bd94 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/releases/tag/release-17.7.1 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/releases/tag/release-18.2.1 cve-icon cve-icon
https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-4c5q-6c64-96j7 cve-icon cve-icon
https://www.vulncheck.com/advisories/umbraco-cms-before-17.7.1-and-18.2.1-missing-authorization-on-signalr-hubs cve-icon cve-icon
History

Fri, 16 Oct 2026 17:45:00 +0000

Type Values Removed Values Added
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.
Title Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubs
First Time appeared Umbraco
Umbraco umbraco Cms
Weaknesses CWE-306
CPEs cpe:2.3:a:umbraco:umbraco_cms:*:*:*:*:*:*:*:*
Vendors & Products Umbraco
Umbraco umbraco Cms
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'}

cvssV4_0

{'score': 6.3, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-16T17:39:00.093Z

Reserved: 2026-10-16T14:31:11.287Z

Link: CVE-2026-111624

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-16T18:17:42.280

Modified: 2026-10-16T19:00:33.600

Link: CVE-2026-111624

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-16T19:30:13Z

Weaknesses