ADV200006 | Type 1 Font Parsing Remote Code Execution Vulnerability

Published: 2020-03-23
MITRE CVE-2020- (TBD)

Microsoft is warning about a vulnerability they have detected used in targeted attacks and that there is no patch for yet. No patch and detected in use, a place for the scary word “zero-day”, but this is not a tabloid.

“Two remote code execution vulnerabilities exist in Microsoft Windows when the Windows Adobe Type Manager Library improperly handles a specially-crafted multi-master font – Adobe Type 1 PostScript format.” This would not be so exciting if not document formats had the feature of including their own fonts in documents.

“There are multiple ways an attacker could exploit the vulnerability, such as convincing a user to open a specially crafted document or viewing it in the Windows Preview pane.”

This affects Windows 10 (but read on), and all Windows Server from 2008 until 2019. Windows 10 has some mitigating features. As always, read the advisory for full details.

There exist no official patch for this as of now. There are some mitigations possible, like “Disable the Preview Pane and Details Pane in Windows Explorer”, “Disable the WebClient service” (WebDAV) and “Rename ATMFD.DLL”. Basefarm has not tested these and recommend everyone to have a test environment that resembles their production environment and test the mitigations before applying them.

Consider the usage of your servers, are there documents viewed on them? Are the documents from an unknown, potentially untrusted source? Do you value the integrity of that server and all it in turn has access too? It might be worth to consider implementing the mitigations. For many servers this use case is not a match and it is potentially better to wait for an official and tested patch.

Basefarm follows this vulnerability internally as BF-VLN-2011507 and asking our dedicated customer teams to follow up these recommendations.