CVE-2026-7886Network attack vector

File permission bypass via unchecked attachment IDs

Published May 21, 2026 · Updated May 21, 2026

IDOR in Concrete CMS 5.0 through 9.5.0 allows remote authenticated users to bypass file permissions through conversation attachments. The AddMessage and UpdateMessage controllers load each user-supplied attachments[] ID with EntityManager::find without calling canViewFile. Any user able to post in a conversation can attach a file-manager object by sequential ID, exposing or linking files outside that user's permissions.

CVSS severity2.3
Low
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IDOR in Concrete CMS 5.0 through 9.5.0 allows remote authenticated users to bypass file permissions through conversation attachments. The AddMessage and UpdateMessage controllers load each user-supplied attachments[] ID with EntityManager::find without calling canViewFile. Any user able to post in a conversation can attach a file-manager object by sequential ID, exposing or linking files outside that user's permissions.

The record

CVE
CVE-2026-7886
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-639, T1213
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=5.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=5.0 <=9.5.0

Published CVSS scores

2.3ConcreteCMSCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1213Data from Information Repositories

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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