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CVE-2026-81909— Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the orphaned-block alias route, allowing an authenticated editor to disclose and force-delete arbitrary blocks

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是Concrete CMS组织的一款灵活易用的企业级内容管理系统。 Concrete CMS 9版本至9.5.2版本存在授权问题漏洞，该漏洞源于block alias路由（concrete/controllers/backend/block/process.php中的Process::alias()）缺少授权验证，未验证引用的block是否确实为目标页面上的孤立块，也未验证调用者是否对源block拥有权限，导致仅被授予自己页面上区域范围add_block_to_area委托的用户可

CVSS 5.9 · Medium EPSS 0.44% · P37

Affected Version Matrix 1

VendorProduct Version RangeStatus
Concrete CMS Concrete CMS 9.0.0≤ 9.5.2 affected
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I. Basic Information for CVE-2026-81909

Vulnerability Information
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Vulnerability Title
Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the orphaned-block alias route, allowing an authenticated editor to disclose and force-delete arbitrary blocks
Source: CVE Program / CVE List V5
Vulnerability Description
Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the block alias route (Process::alias() in concrete/controllers/backend/block/process.php).It does not verify that the referenced block is genuinely orphaned on the target page, nor that the caller holds any permission over the source block. A user granted only an area-scoped add_block_to_area delegation on their own page can therefore pass any block ID on the site: the source block's content is duplicated into an area the rogue editor controls, disclosing that content, and the original block is then force-deleted in the same request, destroying arbitrary site content. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5
Vulnerability Title
Concrete CMS 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Concrete CMS是Concrete CMS组织的一款灵活易用的企业级内容管理系统。 Concrete CMS 9版本至9.5.2版本存在授权问题漏洞，该漏洞源于block alias路由（concrete/controllers/backend/block/process.php中的Process::alias()）缺少授权验证，未验证引用的block是否确实为目标页面上的孤立块，也未验证调用者是否对源block拥有权限，导致仅被授予自己页面上区域范围add_block_to_area委托的用户可
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 9.0.0 ~ 9.5.2 -

II. Public POCs for CVE-2026-81909

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III. Intelligence Information for CVE-2026-81909

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Vendor Pages for CVE-2026-81909 (1)

Same Patch Batch · Concrete CMS · 2026-09-11 · 15 CVEs total

CVE-2026-81907 6.1 MEDIUM Concrete CMS 9.5.2 and below is vulnerable to Cross-Site Request Forgery (CSRF) vin Expres
CVE-2026-81908 6.0 MEDIUM Missing Authorization in Concrete CMS 9.2.0 to 9.5.2 REST API Groups List Endpoint Allows
CVE-2026-18122 6.0 MEDIUM Concrete CMS 9.2.0 to 9.5.2 Express REST API list endpoint exposes restricted Express entr
CVE-2026-68528 6.0 MEDIUM Concrete CMS 9.5.2 and below is vulnerable to Stored XSS in RSS Displayer Block via Unesca
CVE-2026-81910 5.9 MEDIUM Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in The
CVE-2026-81911 5.8 MEDIUM Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot save
CVE-2026-81912 5.7 MEDIUM Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery in the Move Multiple
CVE-2026-81913 5.3 MEDIUM Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL pa
CVE-2026-68526 5.3 MEDIUM Concrete CMS before 9.5.3 is vulnerable to CSRF in the Calendar event duplicate dialog con
CVE-2026-81915 5.1 MEDIUM In Concrete CMS below 9.5.3, Page Type update omits object-level authorization
CVE-2026-81917 5.1 MEDIUM Concrete CMS below 9.5.3 is vulnerable to Stored XSS in the Document Library block file de
CVE-2026-81916 5.1 MEDIUM Incorrect Authorization in the Concrete CMS Express Entries Dashboard below version 9.5.3
CVE-2026-68535 5.1 MEDIUM Concrete CMS 9.2.0 to 9.5.2 is vulnerable to Missing authorization in the Concrete CMS Are
CVE-2026-81918 4.8 MEDIUM Concrete CMS below 9.5.3 is vulnerable to Stored XSS via the Date Format field in the Page

IV. Related Vulnerabilities

Same product: Concrete CMS
Same vendor: Concrete CMS
Same weakness: CWE-862

V. Comments for CVE-2026-81909

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