CVE-2026-86271 Details
Description
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.
A cross-tenant authorization bypass vulnerability has been identified in FluentCMS versions through 0.0.5. The issue resides in the PermissionManager's GetAccessible function, located in the file src/Backend/FluentCMS.Services/Permissions/PermissionManager.cs. This vulnerability allows an authenticated administrator to access and manipulate assets belonging to other sites, violating tenant isolation in multi-site deployments.
To address this vulnerability, it is recommended to key cached authorization data by site ID or reload it for each site evaluation. Additionally, explicit per-site authorization checks should be added to all file and folder read/write operations. Implementing integration tests to ensure that a Site A administrator cannot access Site B objects would also be beneficial.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 7, 2026CISA-ADP
Assessed Sep 9, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/fluentcms/FluentCMS/ | [email protected] | Vendor |
| https://github.com/fluentcms/FluentCMS/issues/2409 | [email protected] | ExploitIssue TrackingTechnical AnalysisVendor |
| https://vuldb.com/cve/CVE-2026-86271 | [email protected] | AdvisoryPermission Required |
| https://vuldb.com/submit/904824 | [email protected] | Issue TrackingPermission Required |
| https://vuldb.com/vuln/399430 | [email protected] | AdvisoryPermission Required |
| https://vuldb.com/vuln/399430/cti | [email protected] | Content Wall |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-862 | Missing Authorization | [email protected] |
| CWE-863 | Incorrect Authorization | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| FluentCMS | <= 0.0.5 (semver) |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 9, 2026 | CVE Modified | CISA-ADP |
| Sep 7, 2026 | New CVE Received | [email protected] |