CVE-2026-27575
📋 TL;DR
This vulnerability in Vikunja task management software allows attackers to compromise accounts through weak password policies and maintain persistent access even after password resets. All self-hosted Vikunja instances prior to version 2.0.0 are affected. The combination of weak authentication controls and session management flaws creates a high-risk scenario.
💻 Affected Systems
- Vikunja
📦 What is this software?
Vikunja by Vikunja
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover leading to data theft, task manipulation, privilege escalation, and persistent backdoor access to the task management system.
Likely Case
Account compromise via credential stuffing or brute-force attacks, allowing unauthorized access to user tasks, projects, and potentially sensitive information.
If Mitigated
Limited impact with proper network segmentation, strong external authentication, and monitoring, though weak passwords remain a risk.
🎯 Exploit Status
Exploitation requires valid user accounts but leverages common attack techniques like credential stuffing and brute-forcing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0.0
Vendor Advisory: https://github.com/go-vikunja/vikunja/security/advisories/GHSA-3ccg-x393-96v8
Restart Required: Yes
Instructions:
1. Backup your Vikunja data and configuration. 2. Update to Vikunja version 2.0.0 or later. 3. Restart the Vikunja service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Enforce Strong Password Policy via External Authentication
allUse external authentication providers (LDAP, OAuth, SAML) that enforce strong password policies
Implement Rate Limiting and Account Lockout
allConfigure web server or application firewall to limit login attempts and lock accounts after failures
🧯 If You Can't Patch
- Implement network segmentation to restrict Vikunja access to trusted users only
- Enable comprehensive logging and monitoring for failed login attempts and suspicious session activity
🔍 How to Verify
Check if Vulnerable:
Check Vikunja version via web interface or configuration files. If version is below 2.0.0, the system is vulnerable.Check Version:
Check Vikunja web interface dashboard or configuration files for version informationVerify Fix Applied:
After updating to 2.0.0 or later, verify that password strength requirements are enforced and that sessions are invalidated after password changes.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from single IP
- Successful logins with weak/common passwords
- Password change events followed by continued session activity from old sessions
Network Indicators:
- Unusual authentication traffic patterns
- Credential stuffing attack patterns
SIEM Query:
source="vikunja" AND (event="login_failed" count>10 OR password="*weak*" OR session_duration>24h)