TI-2026-75410 Aliases CVE-2026-111624 GHSA-q9r6-5jwm-rmgp

Missing authorization in Umbraco CMS SignalR hubs leaks content keys

LOW 28CWE-306Published 2026-10-16 · Updated 2026-10-21

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Attack requirements: Present
Impact type: Security bypass
Confidentiality · integrity · availability: Low · None · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-306.

Summary

Umbraco CMS from 17.0.0 before 17.7.1 and from 18.0.0 before 18.2.1 is affected. The backoffice PreviewHub and BackofficeHub SignalR hubs lack an authorization check, which is CWE-306 (missing authentication for a critical function). An unauthenticated remote attacker can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and the timing of editorial activity.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00309 23rd percentileScored 2026-11-07

Fix Fixed Umbraco-CMS (umbraco): 17.7.1, 18.2.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
umbraco	Umbraco-CMS	17.0.0 to before 17.7.1; 18.0.0 to before 18.2.1	17.7.1, 18.2.1	Patch available	CNA

Umbraco-CMS Vendorumbraco Affected 17.0.0 to before 17.7.1; 18.0.0 to before 18.2.1 Fixed in 17.7.1, 18.2.1 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:umbraco:umbraco_cms::::::::	—	—	umbraco

cpe:2.3:a:umbraco:umbraco_cms:*:*:*:*:*:*:*:* Versions — — ·umbraco

Remediation

Upgrade Umbraco-CMS 17.x to version 17.7.1 and Umbraco-CMS 18.x to version 18.2.1.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Fix · CNA Umbraco-CMS (umbraco) Fixed in 17.7.1, 18.2.1

Timeline

2026-10-16 Threatist record created from CVE-2026-111624
2026-10-16 Alias added: GHSA-q9r6-5jwm-rmgp
2026-10-18 Priority changed: MEDIUM → LOW
2026-10-21 CISA SSVC decision points changed

References

Patch 2

Advisory 1

GitHub Security Advisory (GHSA-4c5q-6c64-96j7)

Other 4

TI-2025-41183 An arbitrary file upload vulnerability in Umbraco CMS v16.3.3 allows attackers to execute… CVSS 3.1CRITICAL 10.0
TI-2012-05477 Umbraco CMS < 4.7.1 codeEditorSave.asmx RCE CVSS 4.0CRITICAL 9.3
TI-2021-22392 Umbraco v8.14.1 - 'baseUrl' SSRF CVSS 4.0MEDIUM 6.9
TI-2024-36846 A stored cross-site scripting (XSS) vulnerability in Umbraco CMS v14.3.1 allows attackers… CVSS 3.1MEDIUM 6.5
TI-2019-15240 Umbraco CMS 4.11.8 through 7.15.10, and 7.12.4, allows Remote Code Execution by… CVSS 3.1HIGH 7.2
TI-2020-04738 Cross-site scripting in Umbraco CMS CVSS 3.1MEDIUM 5.4

See all 75 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences