________________________________________________________________________

                 From the low-hanging-fruit-department
      AVIRA Generic Malformed Container bypass (ISO Container)
________________________________________________________________________

Release mode    : Coordinated disclosure / Vendor does not disclose
CVE             : CVE-2020-9320
Ref             : [TZO-19-2020] - AVIRA Generic AV Bypass (ISO Container)
Vendor          : AVIRA
Status          : PATCHED - Engine version 8.3.54.138.
CVE             : none provided,
Blog            : 
https://blog.zoller.lu/p/from-low-hanging-fruit-department-avira.html
Vulnerability Dislosure Policy: https://caravelahq.com/b/policy/20949

Affected Products
=================
AV Engine below 8.3.54.138

All Avira products :
- Avira Antivirus Server
- Avira Antivirus for Endpoint
- Avira Antivirus for Small Business
- Avira Exchange Security (Gateway)
- Avira Internet Security Suite for Windows
- Avira Prime
- Avira Free Security Suite for Windows
- Cross Platform Anti-malware SDK

Attention:
Avira does not patch or update their very popular command line scanner 
that is still available for download on their website. Since Avira does 
not release and advisory their customers are none the wiser.

Avira licenses it's engine to many OEM Partners. The OEM Partners that 
use the Avira Engine may be vulnerable or not. I would advise that you 
reach out to the vendors listed below to know whether you are affected 
or not. OEM Partners
can reach out to me to retreive the POC in order to test.

AVIRA OEM Partners:
- F-Secure
- Sophos
- Barracude
- Alibaba Cloud Security
- Check Point
- CUJO AI
- TP-Link
- FujiSoft
- AWS
- Rohde and Schwarz
- Careerbuilder
- Huawei
- Dracoon
- Total Availability
- FixMeStick
- APPVISORY
- Tabidus
- Cyren


Source :
https://oem.avira.com/en/partnership/our-partners


I. Background
----------------------------
Quote: "We protect people—like you—across all devices, both directly and 
via our OEM partnerships.We provide a wide variety of best-in-class 
solutions to enhance your protection, performance,
and online privacy—ranging from antivirus to VPN and cleanup technologies.

A server security should get special attention, as a single employee 
might store a malicious file on the network and instantly cause a 
cascading damage across the entire organization.
With Avira's solutions for server security you can prevent such 
scenarios by protecting your network, data, and web traffic. "

Avira has the Trust Seal or the
http://www.teletrust.de/itsmig/


II. Description
----------------------------
The parsing engine supports the ISO container format. The parsing engine 
can be bypassed  by specifically manipulating the ISO Archive
This leads to the Endpoint ignoring the container and the Gateways to 
let this file slip through uninspected.


III. Impact
----------------------------
It bypasses Avira perimeter defenses and sheduled AV scans.

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
----------------------------
PATCHED - Engine version 8.3.54.138.

V. Disclosure timeline
----------------------------

How Avira handled these reports in 2009 :
https://blog.zoller.lu/2009/04/avira-antivir-generic-cab-bypass.html

28 NOV 2019
Submitted the Vulnerabiltiy Details

04 DEC 2019
AVIRA releases a patch but doesn't inform the public and/or customers.