CVE-2026-21879
📋 TL;DR
This CVE describes an Open Redirect vulnerability in Kanboard versions 1.2.48 and below that allows attackers to redirect authenticated users to malicious websites. By crafting URLs like //evil.com, attackers bypass URL validation filters, potentially enabling phishing attacks and credential theft. All users running vulnerable Kanboard versions are affected.
💻 Affected Systems
- Kanboard
📦 What is this software?
Kanboard by Kanboard
⚠️ Risk & Real-World Impact
Worst Case
Attackers successfully redirect authenticated users to convincing phishing sites that steal credentials, leading to account compromise and potential lateral movement within the organization.
Likely Case
Users are redirected to phishing pages or malware distribution sites, resulting in credential theft or malware infections on user devices.
If Mitigated
With proper user awareness training and browser security controls, users might recognize suspicious redirects, limiting successful exploitation.
🎯 Exploit Status
Exploitation requires crafting malicious URLs and tricking authenticated users into clicking them.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.2.49
Vendor Advisory: https://github.com/kanboard/kanboard/security/advisories/GHSA-mhv9-7m9w-7hcq
Restart Required: No
Instructions:
1. Backup your Kanboard installation and database. 2. Download version 1.2.49 from the official repository. 3. Replace the existing installation files with the new version. 4. Verify the update by checking the version in the Kanboard interface.
🔧 Temporary Workarounds
Input Validation Enhancement
allImplement additional URL validation to reject URLs starting with // or containing suspicious patterns.
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block requests containing //evil.com patterns in URLs.
- Educate users about phishing risks and train them to verify URLs before clicking, especially redirects.
🔍 How to Verify
Check if Vulnerable:
Check the Kanboard version in the application settings or by examining the source code; versions 1.2.48 and below are vulnerable.Check Version:
Check the Kanboard web interface under Settings > About, or inspect the version file in the installation directory.Verify Fix Applied:
After updating, confirm the version is 1.2.49 or higher and test URL validation with crafted //evil.com inputs to ensure they are rejected.📡 Detection & Monitoring
Log Indicators:
- Unusual redirect patterns in access logs, such as requests containing // followed by external domains.
Network Indicators:
- Outbound connections to suspicious domains following Kanboard redirects.
SIEM Query:
source="kanboard_access.log" AND url="*//*" AND NOT url="*//localhost*" AND NOT url="*//127.0.0.1*"