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                             CERT-Renater

                 Note d'Information No. 2020/VULN649
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DATE                : 03/12/2020

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running FortiOS, FortiClient versions 6.4,
                                            6.2.

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https://www.fortiguard.com/psirt/FG-IR-20-037%20
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AV Engine evasion via malformed RAR file


Summary

FortiClient and FortiOS AV engines may not immediately detect certain
types of malformed or non-standard RAR archives, potentially containing
malicious files.

Based on the samples provided, FortiClient will detect the malicious
files upon trying extraction by real-time scanning and FortiGate will
detect the malicious archive if Virus Outbreak Prevention is enabled.


Impact

Bypass Protection Mechanism


Affected Products

FortiOS 6.2 running AV engine version 6.00142 and below.

FortiOS 6.4 running AV engine version 6.00144 and below.

FortiClient 6.2 running AV engine version 6.00137 and below.


Solutions

FortiOS 6.2 running AV engine version 6.00145 or later.
FortiOS 6.4 running AV engine version 6.00145 or later.

FortiClient 6.2 running AV engine version 6.00145 or later.
FortiClient 6.4 running AV engine version 6.00243 or later.


Workaround for FortiGate:

Enable Virus Outbreak Prevention feature.


Acknowledgement

Fortinet is pleased to thank Thierry Zoller for reporting this
vulnerability under responsible disclosure.


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+ CERT-RENATER       |    tel : 01-53-94-20-44          +
+ 23/25 Rue Daviel   |    fax : 01-53-94-20-41          +
+ 75013 Paris        |    email:cert@support.renater.fr +
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