The vulnerability was reported by Andrew Lyons and Neel Mehta of Google Inc.
Using the samples provided by Microsoft, Romang scoured GoogleтАЩs cache and found the earliest document that attempted to fetch the exploit dated from February, 2013. The document referenced territory disputes between China and the Philippines.
However, Romang uncovered another Word document created in 2009 that, according to GoogleтАЩs Virus Total service, would also exploit the flaw Microsoft patched. The fileтАЩs title тАЬThe corruption of MahathirтАЭ referred to a Malaysian politician, fitting MicrosoftтАЩs list of possible targets. Both documents to a Bridging Links URL.
The vulnerability might have been spotted in the wild, with campaigns starting as early as 2009. Microsoft believe attacks were limited to Indonesia and Malaysia.
Advisory: SB2013061101 - Remote code execution in Microsoft Office
Vulnerable component: Microsoft Office
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
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The weakness exists due to buffer overflow when processing malicious PNG files. A remote attacker can create specially crafted file, trick the victim into opening it using an affected version of Microsoft Office, trigger memory corruption and execute arbitrary code with privileges of the current user.
Successful exploitation of the vulnerability results in arbitrary code execution on the vulnerable system.
Note: the vulnerability was being actively exploited.