June 14, 2021

Microsoft fixes Internet Explorer zero-day vulnerability

microsoft logoMicrosoft has released eight security bulletins to address 26 different security vulnerabilities in a range of its products including Microsoft Windows, Internet Explorer, SharePoint, .NET Framework, Office, and Silverlight.

The most important patch fixes the zero-day exploit which has been used by attackers in the wild since mid-September. Microsoft reports that there have been targeted attacks aimed at Internet Explorer 8 and 9 however the vulnerability is present in all versions of IE from 6 to IE 11. The vulnerability exists because of a use-after-free coding error in the JavaScript SetMouseCapture implementation in Internet Explorer. Microsoft’s patch (MS13-080) changes “the way that Internet Explorer handles objects in memory” meaning Microsoft fixed the user-after-free bug. The patch is Critical and all users should ensure that it is applied (normally via Windows Update).

The next patch resolves a vulnerability in some Windows kernel-mode drivers, specifically how these drivers handle specially crafted OpenType and  TrueType Font (TTF) files. If exploited the vulnerabilities, which were reported to Microsoft privately, could allow remote code execution and an attacker could take complete control of an affected system. According to Microsoft these bugs exist in all supported releases of Microsoft Windows from XP upwards, except Windows 8.1, Windows Server 2012 R2, and Windows RT 8.1.

Windows is updated again in the next patch (MS13-083) to fix a vulnerability in the Windows Common Control Library that could allow remote code execution. The patch actually updates a fix from 2010 where Microsoft corrected the way in which the Windows common controls handle messages passed from a third-party scalable vector graphics (SVG) viewer. At the time it was rated as Important, but the new patch is rated as Critical for all supported 64-bit editions of Microsoft Windows. The update has no severity rating for Windows RT and for all supported 32-bit editions of Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows 8.

The final Critical level bulletin (MS13-082) fixes two privately reported vulnerabilities and one publicly disclosed vulnerability in Microsoft’s .NET Framework. The worst of the vulnerabilities could allow remote code execution if a user visits a website containing a specially crafted OpenType font (OTF) file using a browser which is able to start XBAP applications. XBAP applications are Windows Presentation Foundation programs that run inside browsers such as Firefox or Internet Explorer. These applications run in a partial sandbox environment.

Microsoft October 2013-Priority.jpg-550x0

The remaining patches are rated as Important:

  • MS13-084 – Vulnerabilities in Microsoft SharePoint Server Could Allow Remote Code Execution. The most severe vulnerability could allow remote code execution if a user opens a specially crafted Office file in an affected version of Microsoft SharePoint Server, Microsoft Office Services, or Web Apps.
  • MS13-085 – Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution. The vulnerabilities could allow remote code execution if a user opens a specially crafted Office file with an affected version of Microsoft Excel or other affected Microsoft Office software.
  • MS13-086 – Vulnerabilities in Microsoft Word Could Allow Remote Code Execution. The vulnerabilities could allow remote code execution if a specially crafted file is opened in an affected version of Microsoft Word or other affected Microsoft Office software. An attacker who successfully exploited the vulnerabilities could gain the same user rights as the current user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
  • MS13-087 – Vulnerability in Silverlight Could Allow Information Disclosure. The vulnerability could allow information disclosure if an attacker hosts a website that contains a specially crafted Silverlight application that could exploit this vulnerability.