SMB: Microsoft Windows SMB2 Client Message Size Overflow

This signature detects attempts to exploit a known remote code execution vulnerability in Microsoft Windows SMB Client. It is due to improper validation of certain SMB fields when parsing transaction responses. Remote unauthenticated attackers can exploit this by enticing a user to connect to a malicious SMB server and sending a specially crafted SMB response to the target machine. A successful attack allows for arbitrary code injection and execution with the privileges of the operating system kernel (Ring 0). Code injection that does not result in execution could crash the target system, and result in a denial-of-service condition.

Extended Description

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.

Affected Products

Microsoft windows_server_2004

References

BugTraq: 39340

CVE: CVE-2020-1472

Short Name

SMB:CLIENT-MESSAGE-OF

Severity

Major

Recommended

False

Recommended Action

Drop

SMB: Microsoft Windows SMB2 Client Message Size Overflow

Extended Description

Affected Products

References

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