CVE-2026-68533

Received Received - Intake

Concrete CMS File Manager Permission Bypass via Attachment Upload

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: ConcreteCMS

Description

Concrete CMS below 9.5.3 conversation attachment uploaded endpoint imported files into the file manager before evaluating the "Add Message Attachments" permission, which was only checked after the file had been stored. A user denied that permission, or an unauthenticated visitor on a guest-posting configuration, could import approved files of allowed types into the file manager. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.

CVSS Scores

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Meta Information

Published

2026-09-15

Last Modified

2026-09-15

Generated

2026-10-06

AI Q&A

2026-09-16

EPSS Evaluated

2026-10-04

NVD

CVE-2026-68533

EUVD

EUVD-2026-79144

Affected Vendors & Products

Vendor	Product	Version / Range
concrete_cms	concrete_cms	to 9.5.3 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-862	The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Attack-Flow Graph

Executive Summary

Concrete CMS versions below 9.5.3 have a flaw where uploaded files via the conversation attachment endpoint are added to the file manager before checking user permissions. This means unauthorized users could upload files that bypass permission restrictions.

Detection Guidance

This vulnerability involves Concrete CMS versions below 9.5.3 improperly handling file attachments. To detect it, check your Concrete CMS version using the command: concrete5 --version or by inspecting the version in the admin panel. If the version is below 9.5.3, the system is vulnerable.

Impact Analysis

An attacker could exploit this to store unauthorized files on the server. This might lead to data leakage, unauthorized access, or further attacks if the imported files contain malicious content.

Compliance Impact

This vulnerability does not directly impact compliance with GDPR or HIPAA as it involves a low-severity permission bypass in Concrete CMS that allows unauthorized file storage but does not expose sensitive data or violate data protection requirements.

Mitigation Strategies

Upgrade Concrete CMS to version 9.5.3 or later immediately. This version addresses the permission check issue for file attachments. After upgrading, verify the fix by testing file upload permissions in a non-production environment first.

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