OAuth 2.0 Authorization Bypass in Concrete CMS

Publication date: 2026-05-21

Last updated on: 2026-05-22

Assigner: ConcreteCMS

Description

For Concrete CMS 9.5.0 and below, OAuth 2.0 Authorization-Code Handler Bypasses Account Status. A user with uIsActive=0 (suspended, banned, terminated employee) can still authenticate via OAuth and receive valid API tokens. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N. Thanks 0x4c616e for reporting.

CVSS Scores

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Meta Information

Published

2026-05-21

Last Modified

2026-05-22

Generated

2026-07-02

AI Q&A

2026-05-22

EPSS Evaluated

2026-06-30

NVD

CVE-2026-7887

EUVD

EUVD-2026-31364

Affected Vendors & Products

Vendor	Product	Version / Range
concretecms	concrete_cms	to 9.5.1 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-1287	The product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type.

Attack-Flow Graph

Executive Summary

This vulnerability affects Concrete CMS version 9.5.0 and below. It involves the OAuth 2.0 Authorization-Code Handler, which bypasses account status checks. Specifically, a user whose account is marked as inactive (such as suspended, banned, or a terminated employee) can still authenticate using OAuth and obtain valid API tokens.

Impact Analysis

The impact of this vulnerability is that users who should no longer have access to the system (inactive or banned users) can still authenticate and gain valid API tokens. This could allow unauthorized access to protected resources or services, potentially leading to data exposure or misuse.

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