CISA, FBI, and the Multi-State Information Sharing and Analysis Center are releasing this joint Cybersecurity Advisory to provide IT infrastructure defenders with TTPs, IOCs, and methods to detect and protect against recent exploitation against Microsoft Internet Information Services web servers. AA23-074A Alert, Technical Details, and Mitigations AA23-074A STIX XML MAR-10413062-1.v1 Telerik Vulnerability in U.S. Government IIS Server Telerik: Exploiting .NET JavaScriptSerializer Deserialization (CVE-2019-18935) ACSC Advisory 2020-004 Bishop Fox CVE-2019-18935: Remote Code Execution via Insecure Deserialization in Telerik UI Volexity Threat Research: XE Group GitHub: Proof-of-Concept Exploit for CVE-2019-18935 Microsoft: Configure Logging in IIS GitHub: CVE-2019-18935 No-cost cyber hygiene services: Cyber Hygiene Services and Ransomware Readiness Assessment. See CISA Insights Mitigations and Hardening Guidance for MSPs and Small- and Mid-sized Businesses for guidance on hardening MSP and customer infrastructure. U.S. DIB sector organizations may consider signing up for the NSA Cybersecurity Collaboration Center’s DIB Cybersecurity Service Offerings, including Protective Domain Name System services, vulnerability scanning, and threat intelligence collaboration for eligible organizations. For more information on how to enroll in these services, email [email protected]  To report incidents and anomalous activity or to request incident response resources or technical assistance related to these threats, contact CISA at [email protected], or call (888) 282-0870, or report incidents to your local FBI field office.