Quick answers
- Is CVE-2026-81920 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-81920 being exploited in the wild.
- How severe is CVE-2026-81920?
- Medium severity, with a CVSS score of 4.3, published 15 September 2026.
- Which products and versions are affected?
- Concrete CMS below 9.5.3.
- Is there a fix for CVE-2026-81920?
- A patch was published on 2026-09-15: Fixed in Concrete CMS 9.5.3 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-81920 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-81920?
- 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
The vulnerability is a CSRF flaw in the dashboard's SEO Excluded Words page reset() controller action. The vulnerable code clears the concrete.seo.exclude_words configuration but fails to validate the anti-CSRF token provided by the reset modal and does not enforce the POST HTTP method, allowing GET-based attacks. An unauthenticated attacker can craft a malicious page containing a request that, when visited by an authenticated user with SEO management permissions, triggers an automatic reset of the reserved-word list. This causes the site's Text urlify service to revert to default URL slug generation rules, silently altering SEO behavior for newly created content. The issue was patched in Concrete CMS 9.5.3.
Affected products
- Concrete CMS Concrete CMS below 9.5.3
Timeline
- 2026-09-15: disclosed
- 2026-09-15: patched: Fixed in Concrete CMS 9.5.3