VulnerabilityAnalyzed

CVE-2026-7886

Concrete CMS 9.5.0 and below is vulnerable to IDOR in AddMessage/UpdateMessage via attachments[] parameter which can lead to file permission bypass.

LOW 2.3EPSS 0.29%

Does this matter?

Lower severity and a low EPSS score (0.29%). Track it; it rarely justifies an emergency change on its own.

Description

Concrete CMS 9.5.0 and below is vulnerable to IDOR in AddMessage/UpdateMessage via attachments[] parameter which can lead to file permission bypass. The `AddMessage` and `UpdateMessage` conversation controllers accept user-supplied file attachment IDs and load files directly via `$em->find(File::class, $attachmentID)` without checking per-file permissions (`canViewFile()`). A user who can post in any conversation can reference any file in the CMS file manager by its sequential ID, effectively bypassing the file permission system. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with a vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Tristan Mandani for reporting. if a site truly has private files, the owner should set up a private storage location https://documentation.concretecms.org/user-guide/editors-reference/dashboard/system-and-maintenance/files/file-storage-locations outside of the webroot so that permissions can be checked on view as well. That way, even if a authorized user attaches a file, or otherwise links to it, unauthorized users won't be able to view the file.

CVSS 4.0: 2.3 LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/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/M
EPSS: 0.29% probability · 21th percentile
CISA KEV: Not listed
Weakness: CWE-639
Affected: concretecms/concrete cms
Source: ff5b8ace-8b95-4078-9743-eac1ca5451de

References

https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notesRelease Notes

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.