Zero-day vulnerability in Microsoft Word

Logic error

Not patched

Trend Micro has issued a report detailing in the wild exploitation of a publicly disclosed vulnerability in Microsoft Word. According to VirusTotal timestamps, the first wave of exploitation began on October 31, 2018. The vulnerability was disclosed on October 25.

Known malware:

TROJ_EXPLOIT.AOOCAI
TSPY_URSNIF.OIBEAO

Vulnerability details

Advisory: SB2018102612 - Remote code execution in Microsoft Word

Vulnerable component: Microsoft Word

CVE-ID:

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H/E:H/RL:U/RC:C

CWE-ID: CWE-20 - Improper input validation

Description:

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The weakness exists due to a logical bug is revealed when embedding a video via the 'online video' feature. A remote attacker can embed a video inside a Word document, edit the XML file named document.xml, replace the video link with a crafted payload created by the attacker which opens Internet Explorer Download Manager with the embedded code execution file and execute arbitrary code with elevated privileges.

Successful exploitation of the vulnerability may result in system compromise.

Note: as of October 31, 2018 the vulnerability is being actively exploited in the wild.

External links:

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.