Date: Thu, 2 Jan 2020 14:50:28 +0100
From: Thierry Zoller <thierry@...ler.lu>
To: fulldisclosure-bounces@...lists.org, submissions@...ketstormsecurity.com,
  bugtraq@...urityfocus.com
Cc: "soc@...cert.gov" <soc@...cert.gov>, info@...cl.lu
Subject: [TZO-02-2020] Kaspersyk Generic Malformed Archive Bypass (ZIP GFlag)


________________________________________________________________________

                 From the low-hanging-fruit-department
        Kaspersky Generic Malformed Archive Bypass (ZIP GFlag)
________________________________________________________________________
Release mode    : Coordinated Disclosure
Ref             : [TZO-02-2019] - Kaspersky Generic Archive Bypass (ZIP)
Vendor          : Kaspersky
Status          : Patched
CVE             : Unknown
Dislosure Policy: https://caravelahq.com/b/policy/20949
Blog            : https://blog.zoller.lu
Vendor Advisory : 
https://support.kaspersky.com/general/vulnerability.aspx?el=12430#021219


Introduction
============
10 years ago I took a look at ways to evade AV/DLP Engine detection by 
using various techniques and released a metric ton of Advisories. 10 
years later after multiple CISO type roles I wanted to deep dive again 
and see how far (or not) the AV  industry has reacted to this class of 
vulnerabilities.

These types of evasions are now actively being used in offensive 
operations [1]. To my surprise with a few exceptions most AV Vendors 
haven't, in some cases I found the very same vulnerabilities that were 
patched and disclosed years ago.

Worse than that is the fact that some vendors that were very 
collaborative in 2008/2009 have now  started to ignore submissions 
(until I threaten disclosure)or are trying to argue that generically 
evading AV detection is not a vulnerability.

A lot of exchanges took place on this matter, for instance one vendor 
argued that this could not be called a vulnerability because it would 
not impact Integrity, Availability or Confidentiality so it can't 
possible be a vulnerability.

Even more bothering to me is how the bu bounty platform have created a 
distorted Reporter/Vendor relationship and mostly are executed to the 
detriment of the customers.I am collecting my experiences and will write 
a blog post about this phenomnon.

There will by many more advisories, hoping that I can finally erradicate 
this bug class and I don't have to come back to this 10 years from now 
again.

[1] 
https://www.bleepingcomputer.com/news/security/specially-crafted-zip-files-used-to-bypass-secure-email-gateways/
https://www.techradar.com/news/zip-files-are-being-used-to-bypass-security-gateways

Affected Products
=================
List of 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 Archve 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
http://blog.zoller.lu/2009/04/case-for-av-bypassesevasions.html

IV. Patch / Advisory
----------------------------
Update to the respective available versions as found at
https://support.kaspersky.com/general/vulnerability.aspx?el=12430#021219


Thanks to Kaspersky for coordinating this vulnerability.

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