CVE-2026-18422 Concrete CMS CVE debrief

Who should care

Defenders and administrators of Concrete CMS installations should assess exposure and prioritize remediation. They should verify the patch status of their installations, restrict Edit Page Multilingual Settings permissions to trusted users, and monitor for changes to translations and language routing to detect potential exploitation. Security teams and vulnerability management teams should also review the vulnerability and plan for necessary updates.

Why it matters

A low-severity vulnerability in Concrete CMS allows authenticated users to alter translations and language routing, requiring defenders to verify and upgrade to a fixed version.

• Verify and restrict user permissions to prevent unauthorized changes
• Upgrade to Concrete CMS version 9.5.3 or later to fix the vulnerability
• Monitor for changes to translations and language routing to detect potential exploitation

Technical summary

The vulnerability exists in the multilingual page assignment backend action, where an authenticated user with Edit Page Multilingual Settings permission can bind an arbitrary page in another locale as a translation and delete legitimate translation pairs. This occurs due to missing destination-side authorization checks and CSRF token validation. The issue affects Concrete CMS versions before 9.5.3, with a CVSS v4.0 score of 2.1, indicating low severity. Defenders should prioritize verifying and upgrading to Concrete CMS version 9.5.3 or later.

Defensive priority

Defenders should prioritize verifying and upgrading to Concrete CMS version 9.5.3 or later, and restrict Edit Page Multilingual Settings permissions to trusted users.

Recommended defensive actions

• Verify and upgrade to Concrete CMS version 9.5.3 or later
• Restrict Edit Page Multilingual Settings permissions to trusted users
• Monitor for unauthorized changes to translations and language routing
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, its CVSS score, and affected versions. The vulnerability was reported by Winston Crooker. Concrete CMS version 9.5.3 or later fixes this issue. Defenders should verify the patch status of their installations and restrict Edit Page Multilingual Settings permissions.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.