Vulnerability in Concrete CMS (CVE-2026-81901)
Summary
Vulnerability in Concrete CMS (CVE-2026-81901). Confidential information can be exposed externally. Exploitable via PUT /ccm/api/1.0/pages/{cID}.
Original description
The description as published by the source.
In Concrete CMS 9.2.0 through 9.5.2, the REST API page update endpoint (PUT /ccm/api/1.0/pages/{cID}) did not enforce page-property, page-template, or page-type authorization. A user granted only content-editing rights on a page could therefore alter its properties, template, and type through the API, and could set the header_extra_content attribute, which is rendered unescaped into the head element of every page, to persist JavaScript that executed in the browser of every visitor, including higher-privileged reviewers who approve the page version. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.2 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai 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-2026-81901 has been found in Concrete CMS.
Attackers can target a specific entry point like PUT /ccm/api/1.0/pages/{cID} over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.7/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Concrete CMS CVE-2026-81901" on the vendor's site.
CVE-2026-81901 (Concrete CMS) — CWE-862 / CVSS v3 8.7
Attack vector: remote (network-reachable)
Attack surface: PUT /ccm/api/1.0/pages/{cID}
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 Concrete CMS. Attackers reach the vulnerable code path via PUT /ccm/api/1.0/pages/{cID}.
Check the vendor advisory for the affected versions of Concrete CMS. Attack surface: PUT /ccm/api/1.0/pages/{cID}.
Severity: High (CVSS 8.7/10). Confidential information can be exposed externally.
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 PUT /ccm/api/1.0/pages/{cID} requests with malformed payloads or SQL meta-characters. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Concrete CMS を使っているサービスとバージョンを洗い出す。
-
2Hunt for indicators of compromise detect
grep 'PUT /ccm/api/1.0/pages/{cID}' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
PUT /ccm/api/1.0/pages/{cID}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 PUT /ccm/api/1.0/pages/{cID} 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