Security Experts:

Unofficial Patches Released for Exploited Windows Font Processing Flaws

ACROS Security’s 0patch service has developed unofficial patches for two actively exploited Windows vulnerabilities for which Microsoft has yet to release fixes.

Microsoft revealed earlier this week that it had become aware of targeted attacks exploiting two Windows zero-days related to the way the Adobe Type Manager library handles Type 1 PostScript fonts.

Adobe told SecurityWeek that the impacted library is exclusively supported by Microsoft and Adobe customers are not at risk.

Hackers can exploit the flaws by convincing users to open specially crafted documents or viewing them in the Windows preview pane. It does not appear possible to exploit the vulnerabilities through Internet Explorer or the Outlook preview pane.

The security holes impact Windows 10, 7, 8.1, Server 2008, Server 2012, Server 2016, Server 2019, and Server, but Windows 10 includes mitigations that significantly lower the risk of attacks.

Patches will likely only be released by Microsoft with its April 2020 security updates, but users can apply workarounds that should prevent exploitation. Windows 7 will also be patched, but the fixes will only be made available by Microsoft to customers with an Extended Security Update (ESU) license.

In the meantime, 0patch has released an unofficial patch that will be available for free until Microsoft rolls out the official fixes — the 0patch fix will then only be available to its paying customers.

0patch has developed fixes for Windows 7 and Windows Server 2008 R2 without ESU. Unofficial patches will also be created for Windows 7 and Server 2008 R2 with ESU, Windows 8.1, and Windows Server 2012. The company’s patch only prevents remote exploitation.

“With this micropatch in place, all applications using Windows GDI for font-related operations will find any Adobe Type 1 PostScript fonts rendered invalid and unable to load,” 0patch explained in a blog post describing its fix.

Related: Unofficial Patches Released for Three Unfixed Windows Flaws

Related: Third-Party Patch Released for Windows Zero-Day

Related: 0patch Promises Support for Windows 7 Beyond January 2020

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.