CVE-2026-25531: Kanboard Auth Bypass Vulnerability

CVE-2026-25531 Overview

CVE-2026-25531 is an authorization bypass vulnerability in Kanboard, a project management software focused on Kanban methodology. Prior to version 1.2.50, the fix for CVE-2023-33968 was incomplete, leaving the TaskCreationController::duplicateProjects() endpoint vulnerable to improper access control. This flaw allows authenticated users to duplicate tasks into projects they do not have permission to access, potentially exposing sensitive project information and compromising data integrity across organizational boundaries.

Critical Impact

Authenticated attackers can bypass project-level access controls to duplicate tasks into unauthorized projects, potentially leaking sensitive information and corrupting project data.

Affected Products

• Kanboard versions prior to 1.2.50
• Self-hosted Kanboard installations without the security patch
• Deployments relying on the incomplete fix from CVE-2023-33968

Discovery Timeline

• February 13, 2026 - CVE-2026-25531 published to NVD
• February 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-25531

Vulnerability Analysis

This vulnerability stems from Missing Authorization (CWE-862) in Kanboard's task duplication functionality. The TaskCreationController::duplicateProjects() endpoint fails to properly validate whether the authenticated user has appropriate permissions for target projects before allowing task duplication operations. This is a classic broken access control issue where the application assumes that because a user is authenticated, they should be able to perform operations across project boundaries.

The vulnerability represents an incomplete remediation of the previously identified CVE-2023-33968, indicating that the original patch did not fully address all affected code paths. The attack requires network access and valid authentication credentials, but no special privileges within the target project are necessary for exploitation.

Root Cause

The root cause is the absence of proper authorization checks in the TaskCreationController::duplicateProjects() method. The controller did not verify whether the requesting user had access to the destination project before executing the task duplication operation. This allowed any authenticated user to specify arbitrary project IDs as targets, effectively bypassing the project-level permission model that Kanboard implements.

Attack Vector

An authenticated attacker can exploit this vulnerability by crafting requests to the task duplication endpoint with project IDs they should not have access to. The attack flow involves:

1. Authenticating to Kanboard with any valid user account
2. Identifying task IDs from projects the attacker has access to
3. Sending duplication requests specifying target project IDs the attacker cannot access
4. Successfully duplicating tasks (including potentially sensitive information) into unauthorized projects

The following code excerpts demonstrate the security patch applied to address this vulnerability:

namespace Kanboard\Controller;

+use Kanboard\Core\Controller\AccessForbiddenException;

/**
 * Duplicate automatic action from another project
 *

Source: GitHub Kanboard Commit

The patch imports the AccessForbiddenException class to properly enforce authorization checks in the affected controllers, ensuring that users without appropriate permissions receive access denied responses.

namespace Kanboard\Controller;

+use Kanboard\Core\Controller\AccessForbiddenException;

/**
 * Project Creation Controller
 *

Source: GitHub Kanboard Commit

Detection Methods for CVE-2026-25531

Indicators of Compromise

• Unusual task duplication activity across project boundaries by users with limited access
• Access logs showing requests to /task/duplicateProjects or similar endpoints with unauthorized project IDs
• Tasks appearing in projects from users who should not have write access
• Anomalous patterns of cross-project data movement in audit logs

Detection Strategies

• Review Kanboard access logs for task duplication requests targeting projects outside the user's authorized scope
• Implement application-layer monitoring to detect cross-project task operations by non-privileged users
• Enable verbose logging on the Kanboard application to capture authorization-related events
• Deploy web application firewall rules to flag suspicious parameter manipulation in duplication endpoints

Monitoring Recommendations

• Configure alerts for failed authorization attempts in Kanboard logs
• Monitor for sudden increases in task duplication operations, especially cross-project activities
• Implement user behavior analytics to detect privilege escalation patterns
• Regularly audit project membership and task ownership for unauthorized changes

How to Mitigate CVE-2026-25531

Immediate Actions Required

• Upgrade Kanboard to version 1.2.50 or later immediately
• Review audit logs for evidence of exploitation prior to patching
• Audit project contents for unauthorized task entries that may have been duplicated by attackers
• Restrict network access to Kanboard instances until patching is complete

Patch Information

The vulnerability has been addressed in Kanboard version 1.2.50. The security fix adds proper authorization checks using the AccessForbiddenException mechanism to ensure users can only duplicate tasks into projects where they have appropriate permissions.

For patch details, refer to the GitHub Kanboard Commit and the GitHub Security Advisory GHSA-vrm3-3337-whp9.

Workarounds

• Implement network-level access controls to limit who can reach the Kanboard instance
• Use a reverse proxy or web application firewall to restrict access to sensitive endpoints
• Temporarily disable the task duplication feature if your organization does not require it
• Review and minimize user accounts with access to multiple projects

# Example: Restrict access to Kanboard at the network level using iptables
# Allow only trusted IP ranges to access the Kanboard server
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP