CVE-2026-68526 Concrete CMS CVE debrief

Who should care

Defenders responsible for Concrete CMS installations, particularly those with add-event permission, should assess exposure and verify their system. They should also review their system for any duplicate CalendarEvents and CalendarEventVersions records and update to 9.5.3 or later if necessary. Additionally, defenders should monitor system for potential abuse of Calendar event duplication.

Why it matters

Defenders should care about CVE-2026-68526 because it allows authenticated users with add-event permission to create duplicate CalendarEvents and CalendarEventVersions records in Concrete CMS before version 9.5.3. This could impact system performance or data integrity. Defenders responsible for Concrete CMS installations should assess exposure, verify their system, and update to 9.5.3 or later if necessary.

• Potential for authenticated users to create duplicate CalendarEvents and CalendarEventVersions records
• Possible impact on system performance or data integrity due to duplicate records
• Need for defenders to verify Concrete CMS version and ensure it is updated
• Possible need for review of system for duplicate records

Technical summary

The vulnerability exists in the Calendar event duplicate dialog controller of Concrete CMS before version 9.5.3. An authenticated user with add-event permission can create duplicate CalendarEvents and CalendarEventVersions records due to the lack of validation of an anti-CSRF token. The vulnerability has been assigned a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. This issue could impact system performance or data integrity. Defenders should assess exposure and verify their system.

Defensive priority

Defenders should prioritize verifying their Concrete CMS version and ensuring it is updated to 9.5.3 or later. They should also review their system for any duplicate CalendarEvents and CalendarEventVersions records.

Recommended defensive actions

• Verify Concrete CMS version and update to 9.5.3 or later
• Review system for duplicate CalendarEvents and CalendarEventVersions records
• Monitor system for potential abuse of Calendar event duplication
• 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
• Review compensating controls for exposed systems while remediation is scheduled and verified
• 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, including its CVSS score and vector. However, the corpus does not establish versions, exploitation, impact, or remediation beyond updating to 9.5.3.

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.