The Patching Friars' AlmanacA calendar of CVE saints

Patron of September 11

ZerologonHoly card for zerologon, generated with AI (Claude, Anthropic) for the Lunario dei Frati Patchatori.CC BY-NC-SA 4.0 00 0000 Zerologon OMNIA EX NIHILO
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Saint Zerologon, Who Showed Up With Only Zeros

Patron of domain controllers, the Netlogon protocol, and everyone who never reboots after Patch Tuesday.

Life

On 11 September 2020 Tom Tervoort of Secura revealed Zerologon, a flaw in the Windows Netlogon protocol. Through a cryptographic mistake, by sending messages full of zeros an attacker on the network could, after a few tries, reset the domain controller's password and seize the whole Active Directory domain. It soon became a favourite tool of ransomware groups.

Prayer

O Saint Zerologon, who conquers the domain with a handful of zeros, let our cryptography never settle for the null vector. Amen.

How to celebrate

Celebrated by installing the Netlogon patches and enforcing secure channels on every controller.

All zeros in a row make a whole domain.

Technical record

Disclosed on
September 11 2020
CVE
CVE-2020-1472
CVSS
5.5Actively exploited (CISA KEV)
Product
Microsoft · Windows Server version 2004

An elevation of privilege vulnerability exists when an attacker establishes a vulnerable Netlogon secure channel connection to a domain controller, using the Netlogon Remote Protocol (MS-NRPC). An attacker who successfully exploited the vulnerability could run a specially crafted application on a device on the network. To exploit the vulnerability, an unauthenticated attacker would be required to use MS-NRPC to connect to a domain controller to obtain domain administrator access. Microsoft is addressing the vulnerability in a phased two-part rollout. These updates address the vulnerability by modifying how Netlogon handles the usage of Netlogon secure channels. For guidelines on how to manage the changes required for this vulnerability and more information on the phased rollout, see How to manage the changes in Netlogon secure channel connections associated with CVE-2020-1472 (updated September 28, 2020). When the second phase of Windows updates become available in Q1 2021, customers will be notified via a revision to this security vulnerability. If you wish to be notified when these updates are released, we recommend that you register for the security notifications mailer to be alerted of content changes to this advisory. See Microsoft Technical Security Notifications.

Sources: cybersecurity.bureauveritas.com

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