Zero-day vulnerability in Microsoft Office

Memory corruption
CVE-2015-1641

The vulnerability accounts for nearly 66% of attacks using Office Word.

APT attacks, targeting Tibetans, Uyghurs, human rights groups in Taiwan and Hong Kong, and journalists.

Vulnerability details

Advisory: SB2015041401 - Multiple vulnerabilities in Microsoft Office

Vulnerable component: Microsoft Office

CVE-ID: CVE-2015-1641

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

CWE-ID: CWE-119 - Memory corruption

Description:

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

The weakness exists due to boundary error when handling rich text format files. A remote attacker can create a specially crafted RTF document, trick the victim into opening it, trigger memory corruption and execute arbitrary code with privileges of the current user.

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: the vulnerability was being actively exploited.

Known APT campaigns:

China-based group KeyBoy

KeyBoy is a threat actor believed to operate from China.

Firstly its malicious activity has been observed in summer 2016 in attacks targeting Tibetan Community. In the hacking campaigns not only against Tibet, but also Hong Kong, Taiwan, and Uyghur the group has been exploiting vulnerabilities CVE-2012-0158╨▒ CVE-2012-1856, CVE-2015-1641 and CVE-2015-1770.

Researchers for Trend Micro linked KeyBoy to Operation Tropic Trooper, campaign targeting Taiwan and the Philippines since 2012.

External links:

https://technet.microsoft.com/en-us/library/security/ms15-033.aspx
http://www.securityweek.com/year-old-office-vulnerabilities-most-popular-current-attacks
https://degsew.wordpress.com/2016/03/28/new-microst-office-word-2007-2013-exploit-cve-2015-1641-anal...
http://news.softpedia.com/news/cve-2015-1641-and-cve-2015-2545-are-today-s-most-popular-microsoft-wo...
http://www.securityweek.com/spear-phishing-attacks-target-industrial-firms-kaspersky-lab-ics-cert
http://www.securitynewspaper.com/2016/07/19/cve-2015-1641-cve-2015-2545-todays-popular-microsoft-wor...

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.