CVE-2026-26274: October CMS SQL Injection Vulnerability

CVE-2026-26274 Overview

A Twig sandbox security policy bypass vulnerability has been identified in October CMS, a popular Content Management System and web platform. This vulnerability allows backend users with Developer permissions to perform unauthorized database write operations when cms.safe_mode is enabled. By exploiting Twig template markup, attackers can execute insert, update, and delete operations on any database table through the query builder that is included in the sandbox allow-list.

Critical Impact

Backend users with Developer permissions can bypass the Twig sandbox security policy to manipulate any database table, potentially leading to data integrity compromise, unauthorized data modification, or complete database destruction.

Affected Products

• October CMS versions prior to 3.7.14
• October CMS versions prior to 4.1.10

Discovery Timeline

• 2026-04-21 - CVE CVE-2026-26274 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-26274

Vulnerability Analysis

This vulnerability stems from an incomplete implementation of the Twig sandbox security policy within October CMS. The sandbox mechanism is designed to restrict what operations can be performed within Twig templates when cms.safe_mode is enabled, providing a layer of protection against malicious template code execution by backend users.

However, the query builder functionality was inadvertently included in the sandbox allow-list, creating a security gap. This oversight enables backend users who possess Developer permissions to craft Twig template markup that directly interfaces with the database through the query builder, completely bypassing the intended write operation restrictions.

The vulnerability is classified under CWE-184 (Incomplete List of Disallowed Inputs), as the sandbox failed to properly restrict all dangerous database operations.

Root Cause

The root cause of this vulnerability lies in the incomplete configuration of the Twig sandbox security policy. When designing the allow-list for safe operations within the sandbox environment, the query builder's write capabilities (insert, update, delete) were not properly excluded. This created an unintended pathway for authenticated users with Developer permissions to execute arbitrary database modifications through Twig templates, even when cms.safe_mode was explicitly enabled to prevent such operations.

Attack Vector

The attack requires network access and high-level privileges (Developer permissions) within the October CMS backend. An attacker with these credentials can:

1. Access the backend template editor or any interface that processes Twig templates
2. Craft malicious Twig template code that utilizes the query builder
3. Execute database write operations (INSERT, UPDATE, DELETE) on any table
4. Modify, corrupt, or delete critical application data including user accounts, configurations, and content

The exploitation complexity is considered high due to the requirement for authenticated access with elevated Developer permissions. However, once these prerequisites are met, the attacker gains unrestricted database write access.

The vulnerability exploits the query builder interface that is available within Twig templates when cms.safe_mode is enabled. Malicious actors can leverage standard query builder methods to target any database table, bypassing the security restrictions that should prevent such operations. For detailed technical information about exploitation patterns, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-26274

Indicators of Compromise

• Unexpected database modifications to critical tables such as user accounts, permissions, or configuration settings
• Unusual Twig template content containing query builder method calls (insert, update, delete)
• Backend activity logs showing Developer users modifying templates with database operation patterns
• Database audit logs revealing write operations originating from template rendering contexts

Detection Strategies

• Implement database activity monitoring to detect unauthorized INSERT, UPDATE, or DELETE operations on sensitive tables
• Review Twig templates for suspicious query builder usage patterns that could indicate exploitation attempts
• Monitor backend user activities, particularly those with Developer permissions accessing template editing interfaces
• Enable detailed logging for template compilation and execution to capture potential malicious payloads

Monitoring Recommendations

• Deploy real-time alerting for any database schema modifications or bulk data changes
• Establish baseline behavior patterns for Developer user activities and alert on anomalies
• Implement file integrity monitoring on template directories to detect unauthorized modifications
• Configure application-level logging to capture all Twig template rendering events with full context

How to Mitigate CVE-2026-26274

Immediate Actions Required

• Upgrade October CMS to version 3.7.14 or later for the 3.x branch immediately
• Upgrade October CMS to version 4.1.10 or later for the 4.x branch immediately
• Audit all user accounts with Developer permissions and remove unnecessary access
• Review database audit logs for any signs of unauthorized write operations
• Inspect existing Twig templates for potentially malicious query builder usage

Patch Information

October CMS has released security patches addressing this vulnerability in versions 3.7.14 and 4.1.10. These updates properly configure the Twig sandbox security policy to exclude database write operations from the allow-list when cms.safe_mode is enabled. Organizations should prioritize upgrading to these patched versions as the primary remediation measure.

For additional details, refer to the GitHub Security Advisory.

Workarounds

• Restrict Developer permissions to only essential personnel until patches can be applied
• Disable cms.safe_mode and implement alternative template restrictions if feasible for your environment
• Implement database-level permissions to restrict write operations from the application service account where possible
• Deploy a Web Application Firewall (WAF) with rules to detect and block query builder patterns in template submissions

# Configuration example - Upgrading October CMS via Composer
# For October CMS 3.x branch:
composer require october/cms:^3.7.14

# For October CMS 4.x branch:
composer require october/cms:^4.1.10

# After upgrade, verify the installed version:
php artisan october:version