CVE-2020-13166: MyLittleAdmin hardcoded machineKey enables pre-auth RCE

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: high.

critical priorityUnauthenticated network-reachable RCE with public exploit code and very high EPSS probability warrants immediate remediation.

What it is

MyLittleAdmin 3.8 ships a hardcoded machineKey in web.config that is identical across all customer installations. Because that key is used to sign and validate ASP.NET ViewState, a remote attacker can craft serialized ASP code that the management tool deserializes and executes. The flaw is pre-authentication and trivially reachable over the network, making it a serious exposure for any internet-facing instance.

Impact

An unauthenticated attacker gains remote code execution in the context of the web application, allowing full compromise of the host and any data reachable from it.

Attack surface

Reached over the network via the management tool's ASP.NET endpoint; the CVSS vector (AV:N/AC:L/PR:N/UI:N) and the advisory title 'preauth RCE' indicate no authentication or user interaction is required.

Exploitation

Public exploit code is referenced by the Packet Storm and SSD advisories, and EPSS is 0.776 (99.5th percentile), indicating high likelihood of exploitation; the CVE is not listed in CISA KEV.

What to do

• Upgrade or patch MyLittleAdmin to a version that does not use a shared hardcoded machineKey; treat 3.8 as unsupported if no fix exists.
• Replace the hardcoded machineKey in web.config with a unique, randomly generated per-installation key.
• Remove MyLittleAdmin from internet-facing exposure; restrict access to trusted management networks or VPN only.
• Enable ViewState MAC validation and disable unsafe deserialization where the platform allows it.
• Rotate any secrets or credentials that may have been exposed if compromise is suspected.

Detection

• Monitor web logs for POST requests to MyLittleAdmin endpoints with unusually large or malformed __VIEWSTATE parameters.
• Alert on ASP.NET worker process spawning child processes such as cmd.exe, powershell.exe or w3wp.exe anomalies.
• Hunt for outbound connections from the web server to unknown hosts following MyLittleAdmin requests.
• Audit web.config files across deployments for the known hardcoded machineKey value.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.