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Vulnerability of Avast Antivirus: buffer overflow of aswSnx.sys

Synthesis of the vulnerability 

An attacker can generate a buffer overflow in aswSnx.sys of Avast, in order to trigger a denial of service, and possibly to run code with system privileges.
Impacted products: Avast AV.
Severity of this bulletin: 2/4.
Creation date: 23/02/2016.
Revision date: 16/06/2017.
Références of this threat: CVE-2015-8620, VIGILANCE-VUL-19011, ZDI-16-681.

Description of the vulnerability 

The Avast product installs the aswSnx.sys (Avast Virtualization) driver.

However, if the size of data is greater than the size of the storage array, an overflow occurs in aswSnx.sys.

An attacker can therefore generate a buffer overflow in aswSnx.sys of Avast, in order to trigger a denial of service, and possibly to run code with system privileges.
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This computer weakness alert impacts software or systems such as Avast AV.

Our Vigil@nce team determined that the severity of this weakness note is medium.

The trust level is of type confirmed by the editor, with an origin of user shell.

A proof of concept or an attack tool is available, so your teams have to process this alert. An attacker with a technician ability can exploit this weakness bulletin.

Solutions for this threat 

Avast Antivirus: version 12.1.
The version 12.1 is fixed.
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