Patch Tuesday: Malicious fonts bedevil Microsoft Windows

Microsoft fixes multiple vulnerabilities in how the company's software renders TrueType fonts

Of the six critical security bulletins Microsoft issued in its Patch Tuesday monthly release of software updates, three address a vulnerability in how Microsoft software renders fonts.

"Fonts have become really complicated," said Wolfgang Kandek, chief technology officer for compliance and security software company Qualys. "There is real processing going on when you print a character, and that complexity can be attacked."

The number of critical bulletins Microsoft released this month is a bit higher than normal, Kandek said. Typically, Microsoft will issue about two or three critical bulletins on Patch Tuesday, which occurs on the second Tuesday of each month. This month half the bulletins -- MS13-052, MS13-053 and MS13-054 -- address how Microsoft systems handle the rendering of TrueType fonts.

With this vulnerability, an attacker can embed malicious values in a font description that would overrun the memory allocated to the font-drawing routine, and write into sections of memory reserved for other operations. The font instructions could be provided to Windows or Internet Explorer (IE) by way of a Web page or a document.

"Depending on where this happens, this can be quite serious," Kandek said.

Windows, for instance, renders all characters onto the screen as a system user, not as a standard user, which has fewer system privileges. An exploit of a font-rendering vulnerability could "go right into the operating system and take control at that level," Kandek said.

Overall, Microsoft issued six critical bulletins, covering Windows OS, the .NET Framework, Silverlight, Office, Visual Studio, Lync and IE. A seventh bulletin, labeled as important, covers the Windows Defender security software.

All six of the critical bulletins include remote code execution vulnerabilities, which can be used to provide attackers with illicit access to machines.

Seventeen of the 34 vulnerabilities covered in the bulletins address IE. "Researchers continue to find flaws in IE, and the attack surface is pretty big," Kandek said, referring to how Microsoft is now supporting five different versions of the browser. The vulnerabilities affect IE versions six through 10 that run on Windows XP, Windows Vista, Windows 7, Windows 8, Windows Server 2003, Windows Server 2008 and Windows RT.

"The major problem there is that users or companies still maintain old versions of the browser. We would be better off if everyone was on the newer version" of IE, Kandek said.

One Windows vulnerability, which affects memory management, has already been publicly revealed, and has been used for an exploit that can run on the Metasploit penetration testing software. Security researchers are urging administrators to update their own versions of Windows XP, Windows Vista, Windows 7, Windows 8 and Windows 2008, Windows 2012 and Windows RT as soon as possible.

"July is one of the uglier releases we've seen from Microsoft this year. To say that all Microsoft products are affected and everything is affected critically is not an overstatement," wrote Lumension security and forensic analyst Paul Henry in an email statement. "It's difficult to prioritize one or two because all the bulletins likely need your attention this Patch Tuesday."

In addition to Microsoft patches, administrators should also take a look at Adobe's monthly set of patches, also released Tuesday. They cover vulnerabilities in Adobe Flash, Shockwave and ColdFusion, which is server-side software for rendering websites.

Joab Jackson covers enterprise software and general technology breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is

Join the CSO newsletter!

Error: Please check your email address.

Tags patchesMicrosoftsecuritypatch managementExploits / vulnerabilitiesmalware

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Joab Jackson

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts