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CISA: Windows Server Netlogon Now Vulnerable to Attack

A "Critical"-rated Netlogon vulnerability in newer Windows Server versions can now be exploited via publicly accessible code, warned the Cybersecurity and Infrastructure Security Agency (CISA) this week.

If left unpatched, CVE-2020-1472 could lead to elevation-of-privilege attacks. A successful exploit could enable domain administrator privileges for an attacker, CISA's announcement noted.

These Netlogon vulnerabilities are present in Windows Server 2019 and Windows Server 2016 products. Last month, an exploit wasn't publicly known, but it is now, according to Will Dormann, a vulnerability analyst at CERT/CC.

"Anybody who has not installed the patch from August's [Microsoft's] Patch Tuesday already is going to be in much worse shape than they already were," Dormann indicated in a Twitter post. His analysis can be found in this U.S. CERT article.

Update 9/15: Information on the vulnerability, dubbed "Zerologon," has been published by Secura, which caused Microsoft to increase its risk score, according to Nick Colyer, a senior product marketing manager at security solutions company Automox.

"The recent critical information released by Secura on the vulnerability dubbed Zerologon, first addressed by Microsoft's August Patch Tuesday security update, goes to show that even after a patch has been released, the research does not end," Colyer said via e-mail. "In this case, Secura has released data to Microsoft, justifying an increase in CVSS scoring to 10 of CVE-2020-1472."

Microsoft previously described a two-step approach to dealing with the Netlogon vulnerability. The first step involves installing a security patch that was released last month, which provides initial protection. The next step will be to turn on enforcement of secure Remote ProtoCol (RPC) for Netlogon, which will happen via a Feb. 9, 2021 patch. Organizations will need to have both patches in place. Otherwise, device users could experience access issues. 

IT pros could have trouble locating vulnerable Netlogon clients in their organizations. Last month, Microsoft proposed using its Azure Sentinel cloud-based security information event management (SIEM) solution with its Insecure Protocols Workbook to find those vulnerabilities.

About the Author

Kurt Mackie is senior news producer for 1105 Media's Converge360 group.

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