Release mode     : Coordinated Disclosure
Ref              : [TZO-05-2020] - Kaspersky Generic Archive Bypass (ZIP Compressed Size)
Vendor           : Kaspersky
Status           : Patched 
CVE              : Unknown
Disclosure Policy:
Blog             :
Vendor Advisory  :

Affected Products
The issue affected Secure Connection product and consumer products in those it is incorporated:

Kaspersky Secure Connection prior to version 4.0 (2020) patch E.
Kaspersky Internet Security prior to version 2020 patch E.
Kaspersky Total Security prior to version 2020 patch E.
Kaspersky Security Cloud prior to version 2020 patch E.

Fixed versions
Kaspersky Secure Connection 4.0 (2020) patch E.
Kaspersky Internet Security 2020 patch E.
Kaspersky Total Security 2020 patch E.
Kaspersky Security Cloud 2020 patch E.

I. Background
Kaspersky Lab is a multinational cybersecurity and anti-virus provider headquartered in Moscow, Russia and operated by a holding company in the United Kingdom. It was founded in 1997 . Kaspersky Lab develops  and sells antivirus, internet security, password management, endpoint security, and other cybersecurity 
products and services.

II. Description
The parsing engine supports the ZIP archive format. The parsing engine can be bypassed  by specifically manipulating an ZIP Archive (Compression Size Flag) so that it can be accessed by an end-user but not the Anti-Virus software. The AV engine is unable to scan the container and gives  the file a "clean" rating. 

I may release further details after all known vulnerable vendors have patched their engines.

III. Impact
Impacts depends on the contextual use of the product and engine within the organisation of a customer. Gateway Products (Email, HTTP Proxy etc) may allow the file through unscanned and give it a clean bill of health. Server side AV software will not be able to discover any code or sample contained within this ISO file and it will not raise suspicion even  if you know exactly what you are looking for (Which is for example great to hide your implants or Exfiltration/Pivot Server).

There is a lot more to be said about this bug class, so rather than bore you with it in
this advisory I provide a link to my 2009 blog post 

IV. Patch / Advisory
Update to the respective available versions as found at

Thanks to Kaspersky for coordinating this vulnerability.