MS Patch Tuesday: 71 Vulns, One Exploited as Zero-Day

The Microsoft Patch Tuesday freight train for October rolled in with fixes for at least 71 security defects in Windows products and components and an urgent warning about a newly discovered zero-day cyberespionage campaign.

The Redmond, Wash. software maker confirmed in-the-wild exploitation of one of the patched bugs — CVE-2021-40449 — in an exploit chain discovered and reported by malware hunters at Kaspersky.

Kaspersky separately said the vulnerability was used in a Chinese-speaking cyber-espionage campaign targeting IT companies, diplomatic entities and military and defense contractors.   

Kaspersky researchers Boris Larin and Costin Raiu documented the findings in a blog post on “MysterySnail” and warned that a second information-disclosure vulnerability that was used by the attacker was not fixed. 

“We discovered that it was using a previously unknown vulnerability in the Win32k driver and exploitation relies heavily on a technique to leak the base addresses of kernel modules. We promptly reported these findings to Microsoft. The information disclosure portion of the exploit chain was identified as not bypassing a security boundary, and was therefore not fixed,” the Kaspersky researchers said.

[ READ: Microsoft Raises Alarm for New Windows Zero-Day Attacks ]

Kaspersky described the issue as a use-after-free vulnerability in the Win32k’s NtGdiResetDC function and said it was intercepted by anti-exploit technologies built into its security product lines..

Microsoft slapped an “important” rating on the flaw and warned that it introduced elevation of privilege risks on unpatched Windows systems.

In total, Redmond shipped patches for 71 documented security vulnerabilities in the flagship Windows OS, the Chromium-based Edge browser, Microsoft Exchange, Microsoft Office Services and SharePoint Server.

Two of the 71 documented vulnerabilities are rated “critical,” Microsoft’s highest severity rating.

Security professionals are urging Windows fleet administrators to pay attention to CVE-2021-26427, a remote code execution flaw in Exchange Server that was reported by the U.S. government’s National Security Agency (NSA).

[ READ: Apple Confirms iOS 15 Zero-Day Exploitation ]

The Microsoft patches come one day after Apple rushed out an urgent iOS mobile platform patch to address a software flaw being “actively exploited” in the wild.

The Cupertino, Calif. device maker confirmed the latest zero-day in an advisory and urged iOS and iPad users to upgrade to the newest iOS 15.0.2.

So far in 2021, there have been 73 documented in-the-wild zero day attacks, the majority hitting vulnerable code in products sold by Microsoft, Apple and Google.

Related: Microsoft Office Zero-Day Hit in Targeted Attacks 

Related: Apple Confirms New Zero-Day Attacks on Older iPhones

Related: Google: Sophisticated APT Group Burned 11 Zero-Days

Related: Apple Ships Urgent Patch for FORCEDENTRY Zero-Days

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Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. He is a journalist and cybersecurity strategist with more than 20 years experience covering IT security and technology trends.
Ryan has built security engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky GReAT. He is a co-founder of Threatpost and the global SAS conference series. Ryan’s career as a journalist includes bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive’s ZDNet, PCMag and PC World.
Ryan is a director of the Security Tinkerers non-profit, and a regular speaker at security conferences around the world.
Follow Ryan on Twitter @ryanaraine.

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