CVE-2026-21880: Kanboard LDAP Injection Vulnerability

CVE-2026-21880 Overview

CVE-2026-21880 is an LDAP Injection vulnerability affecting Kanboard, a project management software focused on Kanban methodology. Versions 1.2.48 and below contain a security flaw in the LDAP authentication mechanism where user-supplied input is directly substituted into LDAP search filters without proper sanitization. This vulnerability allows attackers to enumerate all LDAP users, discover sensitive user attributes, and perform targeted attacks against specific accounts.

Critical Impact

Attackers can exploit this LDAP Injection vulnerability to enumerate LDAP directory users, extract sensitive user attributes, and potentially conduct targeted attacks against specific accounts without authentication.

Affected Products

• Kanboard versions 1.2.48 and below
• Kanboard installations using LDAP authentication

Discovery Timeline

• 2026-01-08 - CVE CVE-2026-21880 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2026-21880

Vulnerability Analysis

This LDAP Injection vulnerability (CWE-90) occurs in Kanboard's LDAP authentication mechanism. The core issue is improper input validation where user-controlled data is incorporated directly into LDAP search filter queries without adequate sanitization or escaping. When users authenticate via LDAP, their input is used to construct search filters that query the directory service. Without proper input handling, attackers can manipulate these filters to alter query logic.

The vulnerability enables unauthenticated network-based attacks that can lead to information disclosure from the LDAP directory. While the confidentiality impact is limited to LDAP user enumeration and attribute discovery, this information can serve as reconnaissance for more sophisticated attacks against the organization's identity infrastructure.

Root Cause

The root cause is insufficient input sanitization in the LDAP authentication code path. User-supplied authentication parameters are directly interpolated into LDAP search filter strings without escaping special LDAP filter characters such as *, (, ), \, and null bytes. This allows attackers to inject additional filter conditions or modify the intended query structure.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker can craft malicious input during the LDAP authentication process to inject arbitrary LDAP filter syntax. By manipulating the filter logic, attackers can:

1. Enumerate all users in the LDAP directory by injecting wildcard patterns
2. Discover sensitive user attributes by probing for specific attribute values
3. Identify high-value target accounts for subsequent attacks
4. Potentially bypass authentication checks depending on the filter construction

The vulnerability enables what is commonly known as "blind LDAP injection" where attackers iteratively probe the directory to extract information based on authentication success or failure responses.

Detection Methods for CVE-2026-21880

Indicators of Compromise

• Unusual LDAP authentication attempts containing special characters like *, (, ), \, or null bytes in username fields
• High volume of failed authentication attempts from a single source targeting LDAP authentication
• LDAP query logs showing malformed or unexpected filter patterns
• Authentication attempts with abnormally long username strings

Detection Strategies

• Monitor LDAP server logs for unusual search filter patterns or syntax errors
• Implement alerting on authentication failures that contain LDAP metacharacters in the username field
• Review web application firewall logs for injection patterns targeting the login endpoint
• Enable verbose logging on the Kanboard application to capture authentication attempts

Monitoring Recommendations

• Configure LDAP server auditing to capture all bind and search operations
• Set up anomaly detection for LDAP query volume spikes from the Kanboard application
• Monitor for enumeration patterns such as sequential or systematic username guessing
• Alert on authentication attempts from unexpected geographic locations or IP ranges

How to Mitigate CVE-2026-21880

Immediate Actions Required

• Upgrade Kanboard to version 1.2.49 or later immediately
• Review LDAP server logs for evidence of exploitation attempts
• Consider temporarily disabling LDAP authentication if upgrade cannot be performed promptly
• Implement network-level access controls to restrict access to the Kanboard login interface

Patch Information

Kanboard has released version 1.2.49 which addresses this LDAP Injection vulnerability. The fix involves proper sanitization of user input before incorporation into LDAP search filters. The security patch can be found in GitHub commit dd374079f7c2d1dab74c1680960e684ff8668586. The updated release is available at Kanboard v1.2.49. For full details, refer to the GitHub Security Advisory GHSA-v66r-m28r-wmq7.

Workarounds

• Implement a Web Application Firewall (WAF) rule to filter LDAP metacharacters from authentication requests
• Restrict network access to the Kanboard application to trusted IP ranges only
• Consider switching to alternative authentication methods (local database, OAuth) until the patch is applied
• Enable rate limiting on authentication endpoints to slow down enumeration attempts

# Example: Verify Kanboard version after upgrade
cat /var/www/kanboard/app/constants.php | grep APP_VERSION
# Should show: define('APP_VERSION', '1.2.49');