CVE-2026-81922 in Concrete CMS
Summary
by MITRE • 09/15/2026
Concrete CMS before 9.5.3 did not enforce a per-page authorization check when reordering pages from the sitemap. In the sitemap Explore dashboard controller, the send_to_top and send_to_bottom reorder tasks ran after only a generic sitemap-access check; the controller loaded the page named by the attacker-controlled cNodeID parameter and changed its display order without verifying that the current user held move or arrange permission on that specific page. Because of this, an authenticated user who could reach the sitemap but had no edit or arrange rights on a given page could still move that page and alter the site's global navigation order. 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 Andrew Gonzalez for reporting.
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Analysis
by VulDB Data Team • 09/15/2026
Concrete CMS versions prior to 9.5.3 contain a critical authorization bypass vulnerability within the sitemap management interface, specifically affecting the page reordering functionality. This flaw arises from an insufficient per-page access control check in the Explore dashboard controller responsible for handling navigation adjustments. When users attempt to reorder pages using the send_to_top or send_to_bottom tasks, the system performs only a generic verification that the user has general access rights to view the sitemap. It fails to validate whether the authenticated user possesses specific permissions, such as move or arrange privileges, on the individual page identified by the cNodeID parameter provided in the request. This architectural oversight allows any authenticated user with basic sitemap visibility to manipulate the structural hierarchy of pages they do not own or have administrative rights over.
The technical root cause lies in the sequence of validation operations within the controller logic. The application loads the target page based on attacker-controlled input and immediately proceeds to update its display order without cross-referencing this action against granular permission sets assigned to that specific node. In a secure implementation, every state-changing operation must verify both global session validity and local object-level authorization. By omitting the latter check for reordering tasks, the software effectively treats all pages as publicly editable by anyone who can view them in the sitemap tree. This represents a classic case of broken access control where privilege escalation is achieved not through exploiting code execution flaws but through misconfigured or missing logical checks on resource-specific actions.
The operational impact of this vulnerability centers on the integrity and usability of the website's global navigation structure. An attacker with low-privileged authenticated credentials can arbitrarily rearrange pages, potentially hiding critical content from users by moving it to inaccessible positions in the hierarchy or promoting irrelevant pages to prominent locations. This manipulation disrupts user experience and can be leveraged for social engineering attacks if specific landing pages are moved to appear more authoritative than they are. Although the CVSS v4.0 score of 2.1 indicates low severity due to the requirement for authentication, the potential for persistent disruption to site navigation remains significant in environments where multiple users have varying levels of content management access but lack strict segregation of duties.
From a classification perspective, this vulnerability aligns with CWE-862 Missing Authorization and CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes within the Common Weakness Enumeration framework. In terms of adversary tactics, it corresponds to ATT&CK technique T1078 Valid Accounts, as exploitation relies on legitimate credentials, and potentially T1484 Domain Policy Modification if used to alter site-wide navigation policies that affect user perception. The vulnerability highlights the importance of implementing granular permission checks for all administrative functions, ensuring that actions modifying object state are validated against specific resource permissions rather than broad role-based access controls alone.
Mitigation strategies primarily involve upgrading Concrete CMS to version 9.5.3 or later, where this authorization logic has been corrected to enforce per-page validation before processing reorder requests. For organizations unable to patch immediately due to compatibility constraints, implementing a web application firewall rule that restricts access to the sitemap controller endpoints for users without explicit arrange permissions can provide temporary relief. Additionally, auditing user roles and ensuring that only trusted administrators have access to sitemap management features reduces the attack surface by limiting the pool of potential actors who could exploit this logic flaw. Regular security reviews should include testing all state-changing API endpoints against unauthorized resource identifiers to prevent similar bypasses in future updates.