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CVE-2026-68527— Concrete CMS 8.3.0 through 9.5.2 is vulnerable to an authorization bypass through user-controlled key (cross-calendar IDOR) in the Calendar event edit dialog

Quick assessment

Affected
Concrete CMS Concrete CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Concrete CMS 版本 8.3.0 至 9.5.2 在日历事件编辑对话框（concrete/controllers/dialog/event/edit.php）中存在一个授权绕过漏洞。该对话框在检查权限时，依据的是请求中提供的日历标识符，而非目标事件所属的日历。因此，拥有单个日历上“添加事件”权限的用户，能够读取并覆盖其无权访问的其他日历中的事件，并且可以删除该事件原始的本地实例。将注入的版本发布到线上日历（此操作会使先前已批准版本降级），此外还需要操作者具备 approve_calendar_event

CVSS 5.9 · Medium

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts

Affected Version Matrix 1

VendorProduct Version RangeStatus
Concrete CMS Concrete CMS 8.3.0≤ 9.5.2 affected
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I. Basic Information for CVE-2026-68527

Vulnerability Information
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Vulnerability Title
Concrete CMS 8.3.0 through 9.5.2 is vulnerable to an authorization bypass through user-controlled key (cross-calendar IDOR) in the Calendar event edit dialog
Source: CVE Program / CVE List V5
Vulnerability Description
Concrete CMS versions 8.3.0 through 9.5.2 are vulnerable to an authorization bypass in the Calendar event edit dialog (concrete/controllers/dialog/event/edit.php). The dialog checked permissions against the calendar identifier supplied in the request rather than the calendar owning the targeted event occurrence. A user with the "Add Event" permission on a single calendar could read and overwrite events on calendars they were not permitted to access, and could delete an event's original local occurrence. Publishing the injected version to the live calendar, which demotes the previously approved version, additionally required the actor's approve_calendar_event workflow rights or an auto-approving workflow. The Concrete CMS Security Team gave this a rank of 5.9 with CVSS 4.0 vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 8.3.0 ~ 9.5.2 -

II. Public POCs for CVE-2026-68527

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III. Intelligence Information for CVE-2026-68527

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Vendor Pages for CVE-2026-68527 (1)

IV. Related Vulnerabilities

Same product: Concrete CMS
Same vendor: Concrete CMS
Same weakness: CWE-639

V. Comments for CVE-2026-68527

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