CVE-2026-25924: Kanboard Plugin RCE Vulnerability

CVE-2026-25924 Overview

CVE-2026-25924 is an Authorization Bypass vulnerability in Kanboard, a project management software focused on Kanban methodology. This security control bypass vulnerability allows an authenticated administrator to achieve full Remote Code Execution (RCE) by exploiting a misconfiguration in the plugin installation backend. Although the application correctly hides the plugin installation interface when the PLUGIN_INSTALLER configuration is set to false, the underlying backend endpoint fails to verify this security setting, creating a dangerous gap between the frontend security controls and backend enforcement.

Critical Impact

An authenticated attacker with administrator privileges can bypass security controls to force the server to download and install a malicious plugin, resulting in arbitrary code execution on the Kanboard server.

Affected Products

• Kanboard versions prior to 1.2.50

Discovery Timeline

• 2026-02-11 - CVE-2026-25924 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2026-25924

Vulnerability Analysis

This vulnerability is classified under CWE-863 (Incorrect Authorization), which occurs when an application fails to properly enforce authorization checks on protected resources. In the case of CVE-2026-25924, Kanboard implements a frontend-only security control that hides the plugin installation UI when PLUGIN_INSTALLER is disabled. However, this security measure is incomplete—the backend API endpoint responsible for plugin installation does not validate the PLUGIN_INSTALLER configuration setting before processing requests.

The attack requires network access and an authenticated administrator account, though user interaction is needed. The vulnerability has a changed scope, meaning a successful exploit can impact resources beyond the vulnerable component itself, potentially affecting the entire server environment where Kanboard is deployed. This allows attackers to install arbitrary plugins containing malicious PHP code, which then executes with the same privileges as the web server process.

Root Cause

The root cause of this vulnerability lies in the inconsistent enforcement of the PLUGIN_INSTALLER security setting. While the frontend correctly checks this configuration to hide the plugin installation interface from administrators, the PluginController backend actions fail to perform the same authorization check. This creates a security-by-obscurity scenario where the underlying functionality remains accessible via direct API requests, bypassing the UI-level restriction entirely.

Attack Vector

The attack vector is network-based and requires an authenticated administrator account. An attacker who has compromised or legitimately obtained administrator credentials can craft HTTP requests directly to the plugin installation endpoint, bypassing the hidden UI. The attacker can then specify a remote URL pointing to a malicious plugin archive, which the server will download and install without verifying the PLUGIN_INSTALLER setting. Once installed, the malicious plugin code executes on the server, granting the attacker full control over the Kanboard instance and potentially the underlying server.

The security patch adds proper authorization checks to the PluginController actions:

namespace Kanboard\Controller;

+use Kanboard\Core\Controller\AccessForbiddenException;
use Kanboard\Core\Plugin\Directory;
use Kanboard\Core\Plugin\Installer;
use Kanboard\Core\Plugin\PluginInstallerException;

Source: GitHub Commit Details

The fix imports the AccessForbiddenException class, which is then used to enforce the PLUGIN_INSTALLER configuration check at the controller level, ensuring that all plugin installation actions are properly gated regardless of how they are invoked.

Detection Methods for CVE-2026-25924

Indicators of Compromise

• Unexpected plugin installations in Kanboard, especially when PLUGIN_INSTALLER is configured as false
• HTTP POST requests to plugin installation endpoints from administrator accounts when the feature should be disabled
• New or unknown plugins appearing in the plugins/ directory without authorized installation
• Web server logs showing direct API calls to /plugin/ endpoints with installation actions

Detection Strategies

• Monitor Kanboard application logs for plugin installation activities when PLUGIN_INSTALLER is disabled
• Implement file integrity monitoring on the Kanboard plugins/ directory to detect unauthorized additions
• Review web server access logs for suspicious POST requests targeting plugin management endpoints
• Configure alerting for any new plugin directory creation events on the server

Monitoring Recommendations

• Enable verbose logging in Kanboard to capture all administrative actions including plugin-related requests
• Deploy endpoint detection and response (EDR) solutions to monitor for suspicious PHP file creation in web directories
• Regularly audit installed plugins against an approved whitelist
• Monitor outbound network connections from the web server that may indicate plugin downloads from external sources

How to Mitigate CVE-2026-25924

Immediate Actions Required

• Upgrade Kanboard to version 1.2.50 or later immediately
• Review installed plugins and remove any unrecognized or suspicious entries
• Audit administrator account activity for signs of unauthorized plugin installation attempts
• Verify that PLUGIN_INSTALLER configuration is set to false in production environments if plugin installation is not required

Patch Information

Kanboard has released version 1.2.50 which addresses this vulnerability by enforcing the PLUGIN_INSTALLER configuration check in the PluginController backend actions. The patch ensures that plugin installation requests are properly rejected when the feature is disabled, regardless of whether the request originates from the UI or direct API calls.

For detailed information about the security fix, see the GitHub Security Advisory GHSA-grch-p7vf-vc4f and the GitHub Release v1.2.50.

Workarounds

• Disable external network access from the Kanboard server to prevent malicious plugin downloads if immediate patching is not possible
• Implement network-level controls to block outbound HTTP requests from the web server
• Restrict administrator account access using IP whitelisting or multi-factor authentication
• Apply web application firewall (WAF) rules to block requests to plugin installation endpoints

# Configuration example - Restrict access to plugin endpoints via Apache .htaccess
<Location "/plugin">
    Require ip 127.0.0.1
    Require ip 10.0.0.0/8
</Location>