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vulnerability note 18524

Excel: use after free via XLSB

Synthesis of the vulnerability

An attacker can invite the victim to open a malicious XLSB file, to force the usage of a freed memory area in Excel, in order to trigger a denial of service, and possibly to run code.
Vulnerable systems: Lync, Office, Access, Office Communicator, Excel, OneNote, Outlook, PowerPoint, Project, Publisher, MOSS, Visio, Word, Skype for Business.
Severity of this threat: 3/4.
Consequences of an attack: user access/rights, denial of service on client.
Pirate's origin: document.
Creation date: 15/12/2015.
Références of this weakness: 3104540, MS15-116, VIGILANCE-VUL-18524, ZDI-15-639.

Description of the vulnerability

The Excel product supports binary files with the ".xlsb" extension.

However, if the file is malformed, Excel frees a memory area before reusing it.

An attacker can therefore invite the victim to open a malicious XLSB file, to force the usage of a freed memory area in Excel, in order to trigger a denial of service, and possibly to run code.
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