CVE-2020-5849: Unraid Authentication Bypass Vulnerability

CVE-2020-5849 is an authentication bypass in Unraid that can let an attacker reach the administrative interface without valid credentials. CISA notes it is chainable with CVE-2020-5847 to achieve remote code execution, so a successful bypass can escalate from unauthorized admin access to full system compromise on exposed hosts.

For IT and security teams running Unraid as a NAS or home-lab/server platform, this matters because the admin interface is a high-value target. Confirm exact affected builds, fixed releases, and deployment guidance against the vendor advisory before acting.

How it works

The weakness is classified under CWE-287 (Improper Authentication) and CWE-697 (Incorrect Comparison). In plain terms, the product fails to enforce authentication correctly for the administrative interface, so an attacker who can reach the service may bypass login checks and obtain admin-level access.

Once that access is gained, the same host may be further abused. CISA states this CVE is chainable with CVE-2020-5847 for remote code execution. Do not assume a specific request path, parameter, or payload; those details must be taken from the vendor advisory and any accompanying technical analysis. Treat any unauthenticated reachability to the Unraid admin UI as a serious exposure until patched and verified.

Am I affected? How to find it in your systems

Unraid is commonly deployed as a storage and virtualization appliance on dedicated hardware or in lab and small-business environments. Inventory every system that presents an Unraid management interface, including those reachable only on internal networks or via VPN.

• Enumerate hosts by asset management, network scans for the Unraid web UI, configuration-management databases, and administrator knowledge of NAS/server builds.
• Record the installed Unraid version and compare it to the fixed versions listed in the vendor advisory; do not rely on version guesses.
• Note whether the administrative interface is exposed to untrusted networks, reverse proxies, or the internet.
• Review access and web-server logs for unauthenticated or anomalous requests to admin endpoints, sudden successful admin sessions without corresponding legitimate logins, and any follow-on activity consistent with code execution or new account creation. Specific indicators of compromise are not provided here; align detection with vendor and CISA guidance.

How to remediate

Patch first. Apply the updates specified by the vendor for Unraid, following their instructions exactly. CISA’s required action is to apply updates per vendor instructions.

• Schedule maintenance, take any recommended backups, install the vendor-supplied fix, and reboot or restart services only as the advisory directs.
• After patching, re-check the running version and confirm the authentication bypass is no longer present using the vendor’s verification steps or a controlled access test.
• Harden the admin interface: restrict it to management networks or VPN, enforce strong unique credentials and multi-factor authentication where supported, and disable unnecessary remote access features.
• If you also track CVE-2020-5847, ensure that related fix is applied so the documented chain to remote code execution is closed.

If you can't patch immediately

Reduce exposure until the vendor update can be installed.

• Segment Unraid hosts so the administrative interface is unreachable from untrusted or general user networks; allow only jump hosts or management subnets.
• Place a reverse proxy or WAF in front of the UI and apply virtual-patching rules that block unauthenticated access patterns described in the advisory (tune carefully to avoid breaking legitimate use).
• Temporarily disable or firewall the web management port if operations allow; use console or out-of-band access for urgent administration.
• Increase monitoring: alert on new admin sessions, configuration changes, unexpected processes, and outbound connections from the Unraid host. Retain logs for later investigation.
• Document the exception and set a firm deadline to patch; compensating controls are not a substitute for the vendor fix.

If your data may have been exposed

Actively exploited authentication-bypass and RCE chains can lead to full host compromise and data theft. If this system was reachable and unpatched during the vulnerable period, assume possible unauthorized admin access, rotate credentials and keys stored on or used by the host, review file shares and backups for tampering, and follow your incident-response process. Known ransomware use is not documented for this CVE in the provided facts; still treat any confirmed intrusion as a potential breach. You can run a free exposure scan of your email addresses against known breach data to see whether associated accounts appear in public dumps while you complete containment and recovery.