CVE-2026-27584
📋 TL;DR
CVE-2026-27584 is an authentication bypass vulnerability in ActualBudget server that allows unauthenticated attackers to access sensitive bank account data through SimpleFIN and Pluggy.ai integration endpoints. This affects all ActualBudget Server users with these integrations configured, exposing bank balances and transaction history. The vulnerability requires the server to be network-accessible.
💻 Affected Systems
- ActualBudget Server
📦 What is this software?
Actual by Actualbudget
⚠️ Risk & Real-World Impact
Worst Case
Complete exposure of all users' financial data including bank balances and transaction history to any internet attacker, potentially leading to financial fraud, identity theft, and privacy violations.
Likely Case
Unauthorized access to financial data by opportunistic attackers scanning for vulnerable instances, resulting in privacy breaches and potential targeted attacks based on financial information.
If Mitigated
Limited exposure if server is properly firewalled and only accessible to trusted networks, reducing attack surface to internal threats only.
🎯 Exploit Status
Simple HTTP requests to unprotected endpoints. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 26.2.1
Vendor Advisory: https://github.com/actualbudget/actual/security/advisories/GHSA-m2cq-xjgm-f668
Restart Required: Yes
Instructions:
1. Update ActualBudget Server to version 26.2.1 or later. 2. Restart the server. 3. Verify authentication is now required for SimpleFIN and Pluggy.ai endpoints.
🔧 Temporary Workarounds
Network Isolation
linuxRestrict network access to ActualBudget Server to trusted IPs only
iptables -A INPUT -p tcp --dport [ACTUAL_PORT] -s [TRUSTED_IP] -j ACCEPT
iptables -A INPUT -p tcp --dport [ACTUAL_PORT] -j DROP
Disable Integrations
allTemporarily disable SimpleFIN and Pluggy.ai integrations
Edit server configuration to remove integration settings
🧯 If You Can't Patch
- Implement strict network access controls to limit server exposure
- Disable SimpleFIN and Pluggy.ai integrations until patching is possible
🔍 How to Verify
Check if Vulnerable:
Attempt unauthenticated HTTP GET request to SimpleFIN or Pluggy.ai endpoints. If data is returned without authentication, system is vulnerable.Check Version:
Check ActualBudget Server version in web interface or server logsVerify Fix Applied:
Attempt same unauthenticated requests after patching. Should receive authentication error or no data.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated requests to /simplefin/* or /pluggy/* endpoints
- Successful data retrieval without authentication logs
Network Indicators:
- Unusual volume of requests to integration endpoints from external IPs
- Data exfiltration patterns from financial endpoints
SIEM Query:
source="actualbudget.logs" AND (uri_path="/simplefin/*" OR uri_path="/pluggy/*") AND auth_status="unauthenticated" AND response_code=200