# CVE-2026-85387: Concrete CMS OAuth REST API authorization bypass

Source: https://junglewise.ai/threats/cve-2026-85387-concrete-cms-oauth-rest-api-authorization-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-85387 · Severity: high · CVSS 7.1 · Published 2026-09-16

Concrete CMS is a content management system used to build and manage websites. A flaw in its OAuth authentication system allowed deactivated, deleted, or locked user accounts to retain full API access via previously issued tokens. This means a user whose account was disabled for security reasons could continue to access and potentially modify website data through the REST API indefinitely.

Technologies: [Concrete CMS](https://junglewise.ai/threats/technologies/concrete-cms). Vendors: [Concrete CMS](https://junglewise.ai/threats/vendors/concrete-cms).

## Quick answers

**Is CVE-2026-85387 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85387 being exploited in the wild.

**How severe is CVE-2026-85387?** High severity, with a CVSS score of 7.1, published 16 September 2026.

**Which products and versions are affected?** Concrete CMS before 9.5.4.

**Is there a fix for CVE-2026-85387?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-85387 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-85387?** Check whether you run Concrete CMS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Concrete CMS before 9.5.4 failed to re-validate account status during OAuth REST API authorization requests. The authorization validator checked only that a bearer token existed, had not expired, and had not been explicitly revoked, but did not verify that the account which issued the token remained active. Deactivating, deleting, or locking a user account did not revoke outstanding OAuth tokens. An attacker with a previously issued token from a deactivated account could access endpoints under /ccm/api/1.0/* with the original account's privileges. The vulnerability requires prior possession of a valid OAuth token and applies only to REST API endpoints. Patches are available in version 9.5.4 and later.

## Affected products

- Concrete CMS Concrete CMS before 9.5.4

## Timeline

- 2026-09-16: disclosed

## References

- [https://github.com/concretecms/concretecms](https://github.com/concretecms/concretecms)
- [https://documentation.concretecms.org/developers/introduction/version-history/954-release-notes](https://documentation.concretecms.org/developers/introduction/version-history/954-release-notes)

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