Alert - Font-Parsing 0-Day affecting Microsoft Windows

Number: AL20-010 – UPDATE 1
Date: 24 March 2020

AUDIENCE

This Alert is intended for IT professionals and managers of notified organizations. Recipients of this information may redistribute it within their respective organizations.

PURPOSE

An Alert is used to raise awareness of a recently identified cyber threat Cyber threatA threat actor, using the internet, who takes advantage of a known vulnerability in a product for the purposes of exploiting a network and the information the network carries. that may impact cyber information assets, and to provide additional detection DetectionThe monitoring and analyzing of system events in order to identify unauthorized attempts to access system resources. and mitigation advice to recipients. The Canadian Centre for Cyber Security Cyber securityThe protection of digital information, as well as the integrity of the infrastructure housing and transmitting digital information. More specifically, cyber security includes the body of technologies, processes, practices and response and mitigation measures designed to protect networks, computers, programs and data from attack, damage or unauthorized access so as to ensure confidentiality, integrity and availability. ("Cyber Centre") is also available to provide additional assistance regarding the content of this Alert to recipients as requested.

UPDATE

On 24 March 2020 Microsoft updated the advisory to provide additional information. In view of existing mitigations found in Windows 10, Microsoft no longer recommends that workarounds be applied to Windows 10 systems for this vulnerability VulnerabilityA flaw or weakness in the design or implementation of an information system or its environment that could be exploited to adversely affect an organization's assets or operations. . Microsoft further clarified that the previously referenced, limited attempts to exploit the vulnerability were carried out against systems running Windows 7.

OVERVIEW

On 23 March 2020 Microsoft disclosed an unpatched, critical vulnerability in Microsoft Windows operating systems. Microsoft further advised that they are aware of limited attempts to exploit Windows 7 systems using this vulnerability.

DETAILS

Microsoft published a Security Advisory on 23 March 2020 that describes a 0-day vulnerability, comprised of a pair of critical vulnerabilities in the Adobe Type Manager Library component of Microsoft Windows operating systems. A remote actor could leverage this vulnerability to perform remote code execution. The Microsoft Security Advisory states that limited and targeted attempts to exploit this vulnerability have been observed.

Remote code execution can take place when the Adobe Type Manager Library improperly handles a specially-crafted multi-master font, Adobe Type 1 PostScript format, when a document is opened by an application or previewed in Windows. There are multiple ways an actor could exploit the vulnerabilities, such as convincing a user to open a specially-crafted document or if a user views the document using the Windows Explorer Preview Pane or Details Pane. The Microsoft Outlook Preview Pane is not a vector for exploiting this vulnerability.

SUGGESTED ACTION

Microsoft has not yet released patches for this issue. The Cyber Centre recommends that organizations review the “Workarounds” section of the Microsoft Security Advisory, referenced below, which lists Microsoft’s suggested mitigations. Microsoft notes that these mitigations are not required for Windows 10 systems.

Recommended mitigations include:
- Disable the Preview Pane and Details Pane in Windows Explorer.
- Disable the WebClient service.
- Rename or remove the Adobe Type Manager DLL (ATMFD.DLL)

The Cyber Centre further recommends monitoring the Microsoft Support website and the Cyber Centre Alerts and Advisories webpage for notification of patches becoming available.

REFERENCES

https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/adv200006

 

NOTE TO READERS

The Canadian Centre for Cyber Security (Cyber Centre) operates as part of the Communications Security Establishment.  We are Canada's national authority on cyber security and we lead the government's response to cyber security events. As Canada's national computer security incident response team, the
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