# CVE-2026-18116

## Summary

- **CVE ID:** CVE-2026-18116
- **Severity:** HIGH
- **CVSS Score:** 7.3 (CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-79
- **Published:** Sep 14, 2026
- **Last Modified:** Sep 15, 2026

## Description

Concrete CMS 8.3.0 to 9.5.2 stored calendar event names without sanitization and rendered them without HTML escaping in the workflow approval and deletion notifications shown in the dashboard "Waiting For Me" block. A registered user permitted to add events to a calendar governed by an approval workflow could submit an event whose name contained a script payload, which then executed in an administrator's browser when the pending request was displayed and could be used to create a new administrator account. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks v01demort for reporting.

## Affected Products

- Concrete CMS — Concrete CMS (8.3.0)

## References

- [CNA](https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.25%
- **EPSS Percentile:** 16.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._