CVE-2026-86271 in FluentCMS
Summary
by MITRE • 09/07/2026
A vulnerability was found in FluentCMS up to 0.0.5. This affects the function GetAccessible of the file src/Backend/FluentCMS.Services/Permissions/PermissionManager.cs. Performing a manipulation results in missing authorization. It is possible to initiate the attack remotely. The exploit has been made public and could be used. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability identified within FluentCMS versions up to 0.0.5 represents a critical failure in access control mechanisms, specifically residing in the GetAccessible function located within the src/Backend/FluentCMS.Services/Permissions/PermissionManager.cs file. This flaw constitutes an authorization bypass that allows attackers to circumvent intended security restrictions and gain unauthorized access to protected resources or administrative functions. The root cause lies in the logic governing how permissions are evaluated, where the system fails to properly validate whether a user possesses the requisite privileges for a specific action before granting it. This type of defect is formally categorized under CWE-285, which describes Improper Authorization, and aligns with ATT&CK technique T1078, Valid Accounts, as well as potential privilege escalation vectors if the bypassed permissions lead to administrative capabilities.
The operational impact of this vulnerability is severe due to its remote exploitability. An attacker can initiate an attack from a distant network location without requiring prior authentication or physical access to the target system. By manipulating input parameters sent to the GetAccessible function, an adversary can trick the application into returning true for permission checks that should have returned false. This effectively neutralizes the security boundary of the CMS platform, allowing malicious actors to perform actions such as modifying content, accessing sensitive user data, or potentially achieving full control over the web server depending on the implementation details of subsequent functions called after this check. The fact that public exploits are available significantly lowers the barrier for entry, enabling less sophisticated threat actors to compromise systems running affected versions with minimal effort.
The response from the project maintainers has been notably slow, as indicated by the lack of engagement despite early issue reports. This delay in patching exacerbates the risk landscape, leaving a wide attack surface exposed during the window between disclosure and remediation. Organizations relying on FluentCMS for content management must treat this vulnerability with high priority given the availability of public proof-of-concept code. Immediate mitigation strategies should include upgrading to a patched version as soon as it is released by the maintainers. In the interim, if an upgrade is not immediately feasible, administrators should consider implementing network-level controls such as Web Application Firewalls configured to detect and block anomalous requests targeting the PermissionManager endpoint. Additionally, restricting access to administrative interfaces via IP whitelisting can provide a layer of defense in depth while waiting for the official fix. Continuous monitoring of application logs for unusual permission check patterns is also recommended to identify potential exploitation attempts early.