Quick answers
- Is CVE-2026-8237 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-8237 being exploited in the wild.
- How severe is CVE-2026-8237?
- Medium severity, with a CVSS score of 4, published 21 May 2026.
- Which products and versions are affected?
- Concrete CMS <= 9.5.0, 9.5.0 and below; concrete5/concrete5 (Packagist) < 9.5.1, ECOSYSTEM:introduced=0,fixed=9.5.1.
- Is there a fix for CVE-2026-8237?
- Yes. concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-8237 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-8237?
- Check whether you run Concrete CMS or concrete5/concrete5 (Packagist) 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.
How to fix
- concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later
composer require concrete5/concrete5:^9.5.1
Technical details
An Insecure Direct Object Reference (IDOR) vulnerability exists in Concrete CMS versions 9.5.0 and below due to missing authorization checks in the `/ccm/frontend/conversations/message_detail` endpoint. An unauthenticated attacker can exploit this by enumerating message identifiers to retrieve the full content of any conversation message. This includes messages from restricted pages, member-only areas, and the moderation queue, as well as file attachments with their associated download URLs. The vulnerability is addressed in version 9.5.1.
Affected products
- Concrete CMS Concrete CMS <= 9.5.0
Identifiers
- CVE-2026-8237
- GHSA-xpgc-7vc2-8725
Timeline
- 2026-05-21: disclosed: NVD Published Date
- 2026-05-22: advisory: GitHub Advisory published
- 2026-06-24: patched: GitHub Advisory reviewed and updated with patch info