SRC-2016-0021 : Microsoft Office Excel BIFFRecord Length Out-of-Bounds Read Remote Code Execution Vulnerability



CVSS Score:

9.3, (AV:N/AC:M/Au:N/C:C/I:C/A:C)

Affected Vendors:


Affected Products:

Office Excel

Vulnerability Details:

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Microsoft Office Excel. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the handling of Excel files (.xls). By providing a malformed file with a specially crafted BIFFRecord Length value, an attacker can cause an out-of-bounds read condition that can be later used to overwrite an object's vftable with an arbitrary value. An attacker could leverage this to execute arbitrary code under the context of the current user.

Vendor Response:

Microsoft has issued an update to correct this vulnerability. More details can be found at:

Disclosure Timeline:

  • 2016-01-19 – Vulnerability reported to vendor
  • 2016-01-29 – Vulnerability confirmed by the vendor
  • 2016-04-12 – Coordinated public release of advisory

Proof of Concept:


This vulnerability was discovered by Steven Seeley of Source Incite