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CVE-2026-87031— Missing authorization in the REST API user creation endpoint in Concrete CMS 9.2.0 through 9.5.3 allows arbitrary account creation

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.

在 Concrete CMS 9.2.0 至 9.5.3 版本中，REST API 的用户创建端点（POST /ccm/api/1.0/users，对应 concrete/src/Api/Controller/Users.php 文件中的 add() 方法）在创建账户前未执行权限检查。因此，任何携带 users:add 权限范围的合法 OAuth 令牌（包括没有关联用户上下文的 client_credentials 令牌）都可以创建处于活跃状态且已验证的用户账户，从而绕过邮箱验证和管理员审批流程。在默认注册设置下，

CVSS 2.1 · Low EPSS 0.34% · P27

Affected Version Matrix 1

VendorProduct Version RangeStatus
Concrete CMS Concrete CMS 9.2.0≤ 9.5.3 affected
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I. Basic Information for CVE-2026-87031

Vulnerability Information
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Vulnerability Title
Missing authorization in the REST API user creation endpoint in Concrete CMS 9.2.0 through 9.5.3 allows arbitrary account creation
Source: CVE Program / CVE List V5
Vulnerability Description
n Concrete CMS 9.2.0 through 9.5.3, the REST API user creation endpoint (POST /ccm/api/1.0/users, the add() method of concrete/src/Api/Controller/Users.php) did not perform a permission check before creating an account. As a result, any valid OAuth token carrying the users:add scope, including a client_credentials token with no associated user context, could create active, validated user accounts, bypassing email verification and administrator approval. Under default registration settings the created accounts could then edit page content, providing a path to stored cross-site scripting and further compromise. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/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:N/VI:L/VA:N/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

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 9.2.0 ~ 9.5.3 -

II. Public POCs for CVE-2026-87031

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III. Intelligence Information for CVE-2026-87031

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Other References for CVE-2026-87031 (1)

Same Patch Batch · Concrete CMS · 2026-09-16 · 6 CVEs total

CVE-2026-85385 7.7 HIGH Concrete CMS below 9.5.4 is vulnerable to Stored XSS via User Timezone Field
CVE-2026-85386 7.3 HIGH Concrete CMS before 9.5.4 stored is vulneratble to cross-site scripting via unauthenticate
CVE-2026-18120 6.3 MEDIUM Missing Authorization in legacy Express entries search endpoint allows disclosure of Expre
CVE-2026-87028 5.3 MEDIUM Cross-Board IDOR in the Board Custom Slot Preview in Concrete CMS 9.0.0 through 9.5.3 Disc
CVE-2026-85387 2.0 LOW Concrete CMS before 9.5.4 allows a deactivated user to retain OAuth-authenticated REST API

IV. Related Vulnerabilities

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