CVE-2023-2258
📋 TL;DR
This vulnerability allows CSV formula injection attacks in alf.io event management software. Attackers can embed malicious formulas in CSV files that execute when opened in spreadsheet applications like Excel, potentially leading to remote code execution. Users of alf.io versions prior to 2.0-M4-2304 who process untrusted CSV files are affected.
💻 Affected Systems
- alf.io
📦 What is this software?
Alf by Alf
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on client systems when victims open malicious CSV files in vulnerable spreadsheet applications, potentially leading to full system compromise.
Likely Case
Data exfiltration, system information disclosure, or denial of service through formula execution in spreadsheet applications.
If Mitigated
Limited impact with proper CSV sanitization and user awareness about opening untrusted files.
🎯 Exploit Status
Exploitation requires user to open malicious CSV file. Proof of concept available in bounty reports.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0-M4-2304 and later
Vendor Advisory: https://github.com/alfio-event/alf.io/commit/94e2923a317452e337393789c9f3192dfc1ddac2
Restart Required: Yes
Instructions:
1. Update alf.io to version 2.0-M4-2304 or later. 2. Apply commit 94e2923a317452e337393789c9f3192dfc1ddac2. 3. Restart the application server.
🔧 Temporary Workarounds
CSV sanitization filter
allAdd input validation to sanitize CSV output by escaping formula characters
Implement CSV escaping for characters like =, +, -, @, \t, \r
File type restriction
allRestrict CSV file uploads or require user confirmation before processing
Add file type validation and user confirmation prompts for CSV operations
🧯 If You Can't Patch
- Disable CSV export/import functionality in alf.io configuration
- Educate users to never open CSV files from untrusted sources in spreadsheet applications
🔍 How to Verify
Check if Vulnerable:
Check alf.io version. If version is earlier than 2.0-M4-2304, test CSV export for formula injection by attempting to export data containing formulas.Check Version:
Check application version in admin interface or configuration filesVerify Fix Applied:
After patching, test CSV export with malicious formula payloads to ensure they are properly escaped.📡 Detection & Monitoring
Log Indicators:
- Unusual CSV export requests, large CSV file generation, errors in CSV processing
Network Indicators:
- CSV file downloads from alf.io with suspicious content patterns
SIEM Query:
source="alf.io" AND ("CSV" OR "export") AND (error OR exception OR suspicious)