CVE-2026-6826: CVE-2026-6826: Concrete CMS 9.5.0 and below is vulnerable to unauthenticated file usage disclosure via m…
concretecms · concrete cms · NVD published 2026-05-22 · posted 2026-05-21 · last modified 2026-07-23
What it is
Concrete CMS 9.5.0 and below is vulnerable to unauthenticated file usage disclosure via missing permission check in the usage controller. Any unauthenticated visitor can request /ccm/system/dialogs/file/usage/{fID} with any file ID and receive a list of every page that references that file, including page IDs, handles, and full URLs. This includes pages that are otherwise restricted by permissions.The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.9 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Eldudareeno for reporting.
| Weakness | CWE-200 |
|---|---|
| CVSS vector | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X (source: ff5b8ace-8b95-4078-9743-eac1ca5451de) |
| ATT&CK tactics | Collection |
Exploitation evidence
First exploit evidence seen: 2026-05-21 (earliest date across the sources below).
Exploited in the wild
No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).
Public exploit code
Metasploit
auxiliary/scanner/http/concrete_cms_file_usage_disclosure: Concrete CMS Unauthenticated File Usage Disclosure (disclosure 2026-05-21)
Sources: Rapid7 Metasploit Framework module metadata.
Defend the Chain
The attack chain for CVE-2026-6826 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.
Pick a red technique card on the board, then choose the defence that stops it.
Defend against T1005 Data from Local System Inferred
Inferred from CWE CWE-200
How to fix it
Fixed versions
- concretecms concrete cms: upgrade to 9.5.1 or later
Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.
Vendor advisories and patches
- https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes (Release Notes)
MITRE ATT&CK mitigations for this chain
- M1057 Data Loss Prevention (for T1005) : Data loss prevention can restrict access to sensitive data and detect sensitive data that is unencrypted.
Detection Generic guidance
- Collection: Watch for bulk reads of databases, file shares or mailboxes by the affected service.
Response checklist Generic guidance
- Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
- Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
- Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
- Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.