CVE-2026-27131: Craft CMS Sprig Information Disclosure Flaw

CVE-2026-27131 Overview

CVE-2026-27131 is an information exposure vulnerability in the Sprig Plugin for Craft CMS, a reactive Twig component framework. Starting in version 2.0.0 and prior to versions 2.15.2 and 3.15.2, admin users and users with explicit permission to access the Sprig Playground could potentially expose security keys, credentials, and other sensitive configuration data. Additionally, the vulnerability allows running the hashData() signing function, which could be leveraged to generate valid signatures for malicious purposes.

Critical Impact

Administrative users can access sensitive security keys and credentials through the Sprig Playground feature, potentially compromising the entire Craft CMS installation and enabling further attacks.

Affected Products

• Sprig Plugin for Craft CMS versions 2.0.0 to 2.15.1
• Sprig Plugin for Craft CMS versions 3.0.0 to 3.15.1

Discovery Timeline

• 2026-03-23 - CVE CVE-2026-27131 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-27131

Vulnerability Analysis

This vulnerability falls under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The Sprig Playground feature, designed as a development and testing tool for Twig components, was accessible in production environments when devMode was disabled. This exposed critical functionality that should only be available during development.

The vulnerability enables authenticated users with Sprig Playground access to retrieve sensitive configuration data including security keys and credentials stored within the Craft CMS configuration. Furthermore, attackers could invoke the hashData() signing function, potentially generating valid cryptographic signatures that could be used to forge authenticated requests or bypass security controls.

The network-accessible nature of this vulnerability, combined with the high confidentiality impact, makes it a significant concern for production Craft CMS installations using the Sprig Plugin.

Root Cause

The root cause stems from insufficient access controls on the Sprig Playground feature. The development-oriented functionality remained fully accessible regardless of the devMode configuration setting, allowing sensitive operations to be performed in production environments where such access should be restricted.

Attack Vector

An attacker with administrative privileges or explicit Sprig Playground permissions can exploit this vulnerability through the network. The attack does not require user interaction and can be performed directly through the Craft CMS administrative interface. Once access to the Sprig Playground is obtained, the attacker can:

1. Query configuration values to extract security keys and credentials
2. Execute the hashData() function to generate valid signatures
3. Leverage exposed credentials for further lateral movement or privilege escalation

The vulnerability primarily impacts confidentiality by exposing sensitive data, with limited integrity impact through the signing function abuse capability.

Detection Methods for CVE-2026-27131

Indicators of Compromise

• Unexpected access to the Sprig Playground endpoint from non-development environments
• Unusual queries or requests targeting configuration data retrieval
• Abnormal invocations of the hashData() function in application logs
• Access attempts to the Sprig Playground from IP addresses not associated with legitimate administrators

Detection Strategies

• Monitor access logs for requests to Sprig Playground endpoints when devMode is disabled
• Implement alerting on unusual administrative activity patterns within Craft CMS
• Review user permissions to identify accounts with unnecessary Sprig Playground access
• Audit configuration access patterns for anomalous data retrieval attempts

Monitoring Recommendations

• Enable comprehensive logging for all Sprig Plugin activities in production environments
• Configure SIEM rules to detect access to development-oriented features in production
• Implement real-time alerting for configuration data access attempts
• Regularly audit administrative user accounts and their associated permissions

How to Mitigate CVE-2026-27131

Immediate Actions Required

• Upgrade Sprig Plugin to version 2.15.2 or 3.15.2 immediately
• Review and restrict user permissions for Sprig Playground access
• Audit logs for any unauthorized access to the Sprig Playground feature
• Rotate security keys and credentials if exposure is suspected

Patch Information

The vulnerability has been addressed in Sprig Plugin versions 2.15.2 and 3.15.2. The fix disables access to the Sprig Playground entirely when devMode is disabled by default. A new configuration option enablePlaygroundWhenDevModeDisabled has been introduced, which defaults to false, ensuring production environments are protected by default.

For detailed patch changes, refer to the GitHub commit 09c9da2 and GitHub commit db18c46. Additional information is available in the GitHub Security Advisory.

Workarounds

• Disable the Sprig Playground feature manually if immediate patching is not possible
• Restrict administrative access to only essential personnel
• Implement network-level access controls to limit who can reach the Craft CMS administrative interface
• Consider enabling devMode restrictions at the web server or firewall level

# Configuration example for Craft CMS config/general.php
# Ensure devMode is disabled in production
return [
    'production' => [
        'devMode' => false,
        // After updating to 2.15.2 or 3.15.2, this setting ensures
        // Sprig Playground remains disabled even if accidentally enabled
        // 'enablePlaygroundWhenDevModeDisabled' => false, // default
    ],
];