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Vulnerabilities

Vulnerability · 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.

Published May 21, 2026 · catalog updated Jul 23, 2026 · concrete cms

Check if you run it

No confirmed exploitation is on record for CVE-2026-7886. EPSS is 0.47%. Act only if a listed version of concrete cms is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Low2.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.47%
Remediation
Not established
Affected products
cpe concretecms/concrete cms

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 and conversation controllers accept user-supplied file attachment IDs and load files directly via without checking per-file permissions ( ). 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe concretecms/concrete cmsversion unspecified

How to fix CVE-2026-7886

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-7886. EPSS is 0.47%. Act only if a listed version of concrete cms is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-639: Authorization Bypass Through User-Controlled Key. EPSS 0.47%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 21, 2026 · NIST NVD

    Detected

    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 and conversation controllers accept user-supplied file attachment IDs and load files directly via without checking per-file permissions ( ). A user who can post in any conversation can reference any file in the CMS file manager by its sequential I

  2. Jul 23, 2026 · NIST NVD

    Updated

    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 and conversation controllers accept user-supplied file attachment IDs and load files directly via without checking per-file permissions ( ). A user who can post in any conversation can reference any file in the CMS file manager by its sequential I

Sources

  • CVE.orgVulnerability recordCVE-2026-7886

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-7886

    30-day exploitation probability 0.5%

    first.org
  • NIST NVDVulnerability recordCVE-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. The and conversation controllers accept user-supplied file attachment IDs and load files directly via

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.