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Vulnerability of Grisoft AVG Anti-Virus: bypassing via RAR, TAR, ZIP

Synthesis of the vulnerability 

An attacker can create an archive containing a virus, which is not detected by Grisoft AVG Anti-Virus.
Vulnerable systems: AVG AntiVirus.
Severity of this threat: 1/4.
Number of vulnerabilities in this bulletin: 6.
Creation date: 21/03/2012.
Références of this weakness: BID-52608, BID-52610, BID-52612, BID-52613, BID-52623, BID-52626, CVE-2012-1443, CVE-2012-1456, CVE-2012-1457, CVE-2012-1459, CVE-2012-1461, CVE-2012-1462, VIGILANCE-VUL-11480.

Description of the vulnerability 

Tools extracting archives accept to extract archives which are slightly malformed. However, Grisoft AVG Anti-Virus does not detect viruses contained in these archives.

A RAR archive containing "MZ" as its first 2 bytes bypasses the detection. [severity:1/4; BID-52612, CVE-2012-1443]

A ZIP archive starting by TAR data bypasses the detection. [severity:1/4; BID-52608, CVE-2012-1456]

A TAR archive with a large size bypasses the detection. [severity:1/4; BID-52610, CVE-2012-1457]

A TAR archive with a header containing a large value bypasses the detection. [severity:1/4; BID-52623, CVE-2012-1459]

A TAR+GZ archive containing two streams bypasses the detection. [severity:1/4; BID-52626, CVE-2012-1461]

A ZIP archive starting by 1024 random bytes bypasses the detection. [severity:1/4; BID-52613, CVE-2012-1462]

An attacker can therefore create an archive containing a virus which is not detected by the antivirus, but which is extracted by extraction tools. The virus is then detected once it has been extracted on victim's computer.
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This cybersecurity weakness impacts software or systems such as AVG AntiVirus.

Our Vigil@nce team determined that the severity of this security vulnerability is low.

The trust level is of type confirmed by a trusted third party, with an origin of document.

This bulletin is about 6 vulnerabilities.

An attacker with a expert ability can exploit this vulnerability bulletin.

Solutions for this threat 

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