CVE-2026-81902 Concrete CMS CVE debrief

Who should care

Defenders responsible for Concrete CMS installations, particularly those with edit permissions on pages, should assess exposure and prioritize patching. Users with edit permissions on pages are at risk of unauthorized content deletion. The vulnerability impacts Concrete CMS 9 through 9.5.2, requiring defenders to verify and apply patches to prevent exploitation. Security teams and vulnerability management teams should also be aware of the potential risks.

Why it matters

Defenders should care about CVE-2026-81902 because it allows a remote attacker to delete content on pages in Concrete CMS 9 through 9.5.2 without proper CSRF token validation, impacting users with edit permissions.

• Potential permanent destruction of content on pages
• Possible deletion of blocks from the global Blocks table and block-type data table
• Required verification of patch application to prevent unauthorized content deletion
• Need for monitoring and restricting access to the block removal panel

Technical summary

Concrete CMS 9 through 9.5.2 did not validate a CSRF token in the orphaned block removal panel action (removeOrphanedBlocks). This oversight allows a remote attacker to delete content on pages without proper validation, impacting users with edit permissions. The vulnerability has a CVSS v4.0 score of 7.1, indicating high severity. The affected product context requires defenders to prioritize verifying and patching Concrete CMS installations to prevent unauthorized content deletion. The technical framing of the vulnerability involves the lack of CSRF token validation, which enables attackers to craft malicious requests.

Defensive priority

Defenders should prioritize verifying and patching Concrete CMS installations to prevent unauthorized content deletion.

Recommended defensive actions

• Verify and apply the patch for Concrete CMS version 9.5.3 or later
• Restrict access to the block removal panel to only trusted users with edit permission
• Monitor for suspicious requests to the block removal panel
• 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, including its CVSS v4.0 score of 7.1. The vulnerability was reported by Yonatan Drori from Tenzai. The official CVE Program record and NVD detail page offer source-provided CVE metadata and vulnerability assessment. The vulnerability affects Concrete CMS installations, particularly those with edit permissions on pages.

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.