CVE-2026-68531: Concrete CMS DOS Vulnerability

CVE-2026-68531 Overview

CVE-2026-68531 is a resource exhaustion vulnerability in Concrete CMS 9 prior to version 9.5.3. The flaw exists in keyword search filters used by the file manager, file folders, and page list. These components fail to escape SQL LIKE wildcard characters before placing user input into database queries. An authenticated user with editor-level or higher privileges can submit a crafted search containing many single-character wildcards. The database then evaluates every row and performs full-table scans, sustaining elevated CPU and I/O on large installations. The Concrete CMS security team assigned this issue [CWE-405] Asymmetric Resource Consumption.

Critical Impact
Authenticated editors can degrade database responsiveness for all users through wildcard-dense searches that trigger full-table scans.

Affected Products

Concrete CMS 9 versions prior to 9.5.3
File manager keyword search component
File folders and page list search filters

Discovery Timeline

2026-09-15 - CVE-2026-68531 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-68531

Vulnerability Analysis

The vulnerability resides in the keyword search filtering logic used across multiple Concrete CMS administrative interfaces. When an authenticated editor submits a search query, the application places the raw keyword input directly into a SQL LIKE clause. The code does not neutralize SQL wildcard metacharacters such as % and _ before query construction. This allows an attacker to craft input consisting predominantly of single-character wildcards.

The database engine must then attempt to match every possible combination against every row in the target table. On installations with large file collections or extensive page hierarchies, the resulting query cost climbs sharply. Repeated wildcard-dense searches sustain elevated database CPU and I/O consumption. Legitimate users experience degraded responsiveness across the platform.

The issue is classified under [CWE-405] Asymmetric Resource Consumption. Unlike SQL injection, the attacker does not exfiltrate or modify data. The impact is confined to availability degradation of the underlying database tier.

Root Cause

The root cause is missing input sanitization for SQL LIKE wildcard metacharacters. While parameterized queries prevent classic SQL injection, they do not automatically escape the % and _ characters that carry special meaning inside LIKE expressions. The Concrete CMS search implementation relied solely on parameterization without wildcard neutralization.

Attack Vector

Exploitation requires network access to the Concrete CMS administrative interface and valid credentials with editor-level or higher privileges. The attacker navigates to the file manager, file folders, or page list search interface. They submit a keyword payload composed of many single-character wildcards. Each request forces a full-table scan. Repeated submissions sustain database resource exhaustion. See the ConcreteCMS 9.5.3 Release Notes for the vendor description.

Detection Methods for CVE-2026-68531

Indicators of Compromise

Repeated search requests to file manager, file folder, or page list endpoints containing high densities of _ or % characters in the keyword parameter
Sustained spikes in database CPU utilization correlated with authenticated editor sessions
Query logs showing LIKE clauses with unusually long wildcard sequences from application service accounts

Detection Strategies

Enable slow query logging on the Concrete CMS database and alert on repeated full-table scans against file and page tables
Inspect web server access logs for search endpoints receiving keyword parameters with abnormal character composition
Correlate authenticated editor session activity with database performance metrics to identify abusive query patterns

Monitoring Recommendations

Track database CPU, I/O wait, and query duration percentiles over time to establish baselines
Monitor for editor accounts issuing high-frequency search requests within short intervals
Alert on any LIKE clause containing more than a threshold count of wildcard characters in application query logs

How to Mitigate CVE-2026-68531

Immediate Actions Required

Upgrade all Concrete CMS 9 installations to version 9.5.3 or later
Audit editor-level and higher accounts to confirm only trusted users hold these privileges
Review database performance dashboards for evidence of prior wildcard abuse

Patch Information

Concrete CMS resolved this vulnerability in version 9.5.3. The fix escapes SQL LIKE wildcard metacharacters in keyword search filters before query execution. Administrators should review the ConcreteCMS 9.5.3 Release Notes and apply the update.

Workarounds

Restrict editor-level and higher access to a minimal set of vetted users until the patch is applied
Enforce rate limiting on search endpoints at the reverse proxy or web application firewall layer
Configure database query timeout thresholds to terminate long-running searches automatically

bash

# Example nginx rate limiting for Concrete CMS search endpoints
limit_req_zone $binary_remote_addr zone=cms_search:10m rate=10r/m;

location ~ ^/(dashboard/files|dashboard/pages) {
    limit_req zone=cms_search burst=5 nodelay;
    proxy_pass http://concretecms_backend;
}