New 0-Day Attack Targeting Windows Users With Microsoft Office Documents
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2021-40444 | Remote Code Execution via MSHTML Rendering Engine in Microsoft Windows/Office (CVE-2021-40444) CVE-2021-40444 is a remote code execution vulnerability in the Microsoft MSHTML browser rendering engine, which Microsoft Office documents can load on Windows systems. It is triggered when a user is convinced to open a specially crafted Office document containing a malicious ActiveX control hosted by the MSHTML engine (tracked as a path-traversal-class issue, CWE-22). A successful attacker gains the ability to run arbitrary code in the context of the logged-on user, with greater impact when that user has administrative rights. Any Windows system that can open Office documents is exposed, spanning Windows 7, 8.1, RT 8.1, Windows 10 (1507 through 21H1) and Windows Server 2004/2008. Exploitation is confirmed in the wild: Microsoft observed targeted attacks at disclosure, the flaw is in CISA's KEV with known ransomware use, and Microsoft released security updates on September 14, 2021. Do: Apply Microsoft's security updates released September 14, 2021 for your Windows version immediately; this is a CISA KEV item with known ransomware use, so patching is treated as mandatory. As interim protection, keep Microsoft Defender Antivirus/Defender for Endpoint signatures current (enterprise detection build 1.349.22.0 or newer, with alerts appearing as 'Suspicious Cpl File Execution') and avoid opening untrusted Office documents, since exploitation requires user interaction with a crafted file. | 8.8 | 97% | KEV ransomware PoC ×2 |
| masshundreds of millions of Windows PCs and servers (nearly all Windows desktop/laptop installs on affected versions at disclosure) |
Full article395 words · extracted from thehackernews.com · click to collapse
Ravie LakshmananSep 08, 2021
Microsoft on Tuesday warned of an actively exploited zero-day flaw impacting Internet Explorer that's being used to hijack vulnerable Windows systems by leveraging weaponized Office documents.
Tracked as CVE-2021-40444 (CVSS score: 8.8), the remote code execution flaw is rooted in MSHTML (aka Trident), a proprietary browser engine for the now-discontinued Internet Explorer and which is used in Office to render web content inside Word, Excel, and PowerPoint documents.
"Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents," the company said.
"An attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document. 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," it added.
The Windows maker credited researchers from EXPMON and Mandiant for reporting the flaw, although the company did not disclose additional specifics about the nature of the attacks, the identity of the adversaries exploiting this zero-day, or their targets in light of real-world attacks.
EXPMON, in a tweet, noted it found the vulnerability after detecting a "highly sophisticated zero-day attack" aimed at Microsoft Office users, adding it passed on its findings to Microsoft on Sunday. "The exploit uses logical flaws so the exploitation is perfectly reliable (& dangerous)," EXPMON researchers said.
However, it's worth pointing out that the current attack can be suppressed if Microsoft Office is run with default configurations, wherein documents downloaded from the web are opened in Protected View or Application Guard for Office, which is designed to prevent untrusted files from accessing trusted resources in the compromised system.
Microsoft, upon completion of the investigation, is expected to either release a security update as part of its Patch Tuesday monthly release cycle or issue an out-of-band patch "depending on customer needs." In the interim, the Windows maker is urging users and organizations to disable all ActiveX controls in Internet Explorer to mitigate any potential attack.
Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post.
Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2021/09/new-0-day-attack-targeting-windows.html