Vulnerability in Concretecms (CVE-2026-87031)
Summary
Vulnerability in Concretecms (CVE-2026-87031). Risk of unauthorized operations or information disclosure. Exploitable via POST /ccm/api/1.0/users.
Original description
The description as published by the source.
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: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-87031 has been found in Concretecms.
Attackers can target a specific entry point like POST /ccm/api/1.0/users over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 2.7/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Concretecms CVE-2026-87031" on the vendor's site.
CVE-2026-87031 (Concretecms) — CWE-862 / CVSS v3 2.7
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /ccm/api/1.0/users
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-862) exists in Concretecms. Attackers reach the vulnerable code path via POST /ccm/api/1.0/users.
Check the vendor advisory for the affected versions of Concretecms. Attack surface: POST /ccm/api/1.0/users.
Severity: Low (CVSS 2.7/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /ccm/api/1.0/users requests with malformed payloads or SQL meta-characters. Run grep -r 'Concretecms' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Concretecms' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Concretecmsを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /ccm/api/1.0/users' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /ccm/api/1.0/usersへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Post-deployment verification verify
Replay attack against POST /ccm/api/1.0/users on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
References
- web documentation.concretecms.org
- web nvd.nist.gov
- web github.com