Microsoft Patches IE Zero-Day Among 74 Vulnerabilities

Patch Tuesday is back once again, bringing with it 74 security fixes, 61 of which are classified as Important and 13 as Critical, including one Internet Explorer bug under active attack.

Microsoft today released fixes for CVEs across Windows, Internet Explorer, Microsoft Edge, Office and Office 365, ChakraCore, Exchange Server, Open Source Software, and Visual Studio.

The vulnerability currently being exploited in the wild is CVE-2019-1429, a scripting engine memory corruption vulnerability in Internet Explorer. A remote code execution flaw exists in the way the scripting engine handles objects in memory in IE, and it could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user.

Attackers who successfully exploited this vulnerability could gain the same user rights as the current user. If the user is logged in with administrator privileges, the attackers could exploit the vulnerability to take control of an affected system. From there, they could install programs; view, edit, or delete data; or create new accounts with full user rights.

To do this, the attackers could host a website designed to exploit the bug through Internet Explorer and convince the target to visit the site. Alternatively, they could embed an ActiveX control labeled "safe for initialization" within an app or Office document that hosts the IE rendering engine and trick someone into opening it. In the latter scenario, the victim wouldn't need to use IE to be infected, meaning they should patch even if they don't rely on the browser.

Today's patch fixes the flaw, reported by Clément Lecigne of Google's Threat Analysis Group, by changing the way the Internet Explorer scripting engine handles objects in memory.

"Security training on common phishing and user-targeted attack methods could further reduce the risk of this vulnerability being exploited, but as it is already being exploited in the wild, it is highly recommended to get the patch rolled out quickly to resolve the vulnerability completely," says Chris Goettl, director of security product management at Ivanti.

Microsoft also patched four Critical flaws (CVE-2019-1389, CVE-2019-1397, CVE-2019-1398, CVE-2019-0721) in Hyper-V and Hyper-V Network Switch. These would enable an authenticated user on a guest system to run potentially malicious code on the host. "Microsoft notes that exploitation of these vulnerabilities is less likely, but these patches should still be prioritized for all Hyper-V systems," says Jimmy Graham, director of product management at Qualys.

Today's roundup included a fix for CVE-2019-1457, a security feature bypass bug that exists in Office for Mac due to improper enforcement of macro settings in Excel files. To exploit this, an attacker would have to embed a control in an Excel worksheet that specifies a macro should be run, and then convince a user to open a specially crafted file with an affected version of Excel. This update fixes the vulnerability by enforcing macro settings on Excel documents.

Also worth noting is Microsoft's advisory ADV190024 on a vulnerability in certain Trusted Platform Module (TPM) chipsets from STMicroelectronics. This is a TPM firmware flaw, not a vulnerability in the Windows operating system or any specific application. The vulnerability affects key confidentiality in the ECDSA cipher; a firmware update to TPM may be needed.

"Currently no Windows systems use the vulnerable algorithm," Microsoft says. "Other software or services you are running might use this algorithm. Therefore if your system is affected and requires the installation of TPM firmware updates, you might need to re-enroll in security services you are running to remediate those affected services."

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