CVE-2021-3985
📋 TL;DR
CVE-2021-3985 is a cross-site scripting (XSS) vulnerability in Kimai2 time-tracking software that allows attackers to inject malicious scripts into web pages viewed by other users. This affects all Kimai2 users who access the vulnerable interface. Successful exploitation could lead to session hijacking, credential theft, or unauthorized actions.
💻 Affected Systems
- Kimai2
📦 What is this software?
Kimai2 by Kimai
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal administrator credentials, take over accounts, manipulate time-tracking data, or redirect users to malicious sites.
Likely Case
Session hijacking leading to unauthorized access to time-tracking data and potential data manipulation.
If Mitigated
Limited impact with proper input validation and output encoding in place.
🎯 Exploit Status
XSS vulnerabilities are commonly exploited and proof-of-concept details are available in public references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Commit 76e09447c85e762882126b49626a4fe4d93fe8b5 or later
Vendor Advisory: https://github.com/kevinpapst/kimai2/commit/76e09447c85e762882126b49626a4fe4d93fe8b5
Restart Required: No
Instructions:
1. Update Kimai2 to the latest version or at least commit 76e09447c85e762882126b49626a4fe4d93fe8b5. 2. Run 'composer install --no-dev' to update dependencies. 3. Clear cache with 'bin/console cache:clear'.
🔧 Temporary Workarounds
Input Validation Filter
allImplement server-side input validation to sanitize user inputs before processing.
Implement input validation in affected PHP files to filter script tags and special characters
Content Security Policy
allImplement CSP headers to restrict script execution sources.
Add 'Content-Security-Policy: default-src 'self'; script-src 'self'' to web server configuration
🧯 If You Can't Patch
- Implement a web application firewall (WAF) with XSS protection rules
- Disable or restrict access to vulnerable Kimai2 interfaces
🔍 How to Verify
Check if Vulnerable:
Check Kimai2 version against commit hash 76e09447c85e762882126b49626a4fe4d93fe8b5. If running older version, you are vulnerable.Check Version:
git log --oneline -1Verify Fix Applied:
Verify current commit hash matches or is newer than 76e09447c85e762882126b49626a4fe4d93fe8b5 using 'git log --oneline -1'.📡 Detection & Monitoring
Log Indicators:
- Unusual POST/GET requests with script tags or JavaScript payloads in Kimai2 access logs
- Multiple failed XSS attempts in web server logs
Network Indicators:
- HTTP requests containing <script> tags or JavaScript code to Kimai2 endpoints
- Unexpected redirects from Kimai2 pages
SIEM Query:
source="kimai_access.log" AND ("<script>" OR "javascript:" OR "onerror=" OR "onload=")