CVE-2026-81923 Concrete CMS CVE debrief

Who should care

Defenders responsible for Concrete CMS installations, particularly those with bulk SEO tool access configured, should assess exposure and prioritize upgrading to version 9.5.3 or later.

Why it matters

A low-severity vulnerability in Concrete CMS before version 9.5.3 allows users with bulk SEO tool access and view-only permissions to modify meta tags and URLs of pages they cannot edit, potentially impacting content presentation and live URLs. Defenders should prioritize verifying and upgrading to Concrete CMS version 9.5.3 or later, and restrict bulk SEO tool access to authorized users.

• Potential unauthorized modifications to content presentation and live URLs
• Required verification of user access controls and bulk SEO tool configurations
• Need for timely upgrade to Concrete CMS version 9.5.3 or later

Technical summary

The SEO Bulk Update Meta Tags editor in Concrete CMS before 9.5.3 did not check per-page edit permissions before saving, allowing users with bulk SEO tool access and view-only permissions to modify meta tags and URLs of pages they cannot edit. This issue could lead to unauthorized modifications of content presentation and live URLs. The vulnerability was scored 2.1 using CVSS v4.0 vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N by the Concrete CMS security team. 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 bulk SEO tool access to authorized users.

Recommended defensive actions

• Verify and upgrade to Concrete CMS version 9.5.3 or later
• Restrict bulk SEO tool access to authorized users
• Monitor for unauthorized changes to meta tags and URLs
• 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 vulnerability was reported by Andrew Gonzalez and scored 2.1 by the Concrete CMS security team using CVSS v4.0 vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. The evidence is based on the official CVE Program record and NIST NVD detail page. Defenders should verify the affected scope and prioritize upgrading to Concrete CMS version 9.5.3 or later.

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.