FortiOS / FortiProxy - Heap buffer underflow in administrative interface

[SeedTheNet]

https://www.fortiguard.com/psirt/FG-IR-23-001

Summary

A buffer underwrite ('buffer underflow') vulnerability in FortiOS & FortiProxy administrative interface may allow a remote unauthenticated attacker to execute arbitrary code on the device and/or perform a DoS on the GUI, via specifically crafted requests.

 

Exploitation status:

Fortinet is not aware of any instance where this vulnerability was exploited in the wild. We continuously review and test the security of our products, and this vulnerability was internally discovered within that frame.

Affected Products

FortiOS version 7.2.0 through 7.2.3
FortiOS version 7.0.0 through 7.0.9
FortiOS version 6.4.0 through 6.4.11
FortiOS version 6.2.0 through 6.2.12
FortiOS 6.0 all versions
FortiProxy version 7.2.0 through 7.2.2
FortiProxy version 7.0.0 through 7.0.8
FortiProxy version 2.0.0 through 2.0.12
FortiProxy 1.2 all versions
FortiProxy 1.1 all versions

 

Even when running a vulnerable FortiOS version, the hardware devices listed below are *only* impacted by the DoS part of the issue, *not* by the arbitrary code execution (non-listed devices are vulnerable to both): 

 

FortiGateRugged-100C
FortiGate-100D
FortiGate-200C
FortiGate-200D
FortiGate-300C
FortiGate-3600A
FortiGate-5001FA2
FortiGate-5002FB2
FortiGate-60D
FortiGate-620B
FortiGate-621B
FortiGate-60D-POE
FortiWiFi-60D
FortiWiFi-60D-POE
FortiGate-300C-Gen2
FortiGate-300C-DC-Gen2
FortiGate-300C-LENC-Gen2
FortiWiFi-60D-3G4G-VZW
FortiGate-60DH
FortiWiFi-60DH
FortiGateRugged-60D
FortiGate-VM01-Hyper-V
FortiGate-VM01-KVM
FortiWiFi-60D-I
FortiGate-60D-Gen2
FortiWiFi-60D-J
FortiGate-60D-3G4G-VZW
FortiWifi-60D-Gen2
FortiWifi-60D-Gen2-J
FortiWiFi-60D-T
FortiGateRugged-90D
FortiWifi-60D-Gen2-U
FortiGate-50E
FortiWiFi-50E
FortiGate-51E
FortiWiFi-51E
FortiWiFi-50E-2R
FortiGate-52E
FortiGate-40F
FortiWiFi-40F
FortiGate-40F-3G4G
FortiWiFi-40F-3G4G
FortiGate-40F-3G4G-NA
FortiGate-40F-3G4G-EA
FortiGate-40F-3G4G-JP
FortiWiFi-40F-3G4G-NA
FortiWiFi-40F-3G4G-EA
FortiWiFi-40F-3G4G-JP
FortiGate-40F-Gen2
FortiWiFi-40F-Gen2

Solutions

Please upgrade to FortiOS version 7.4.0 or above
Please upgrade to FortiOS version 7.2.4 or above
Please upgrade to FortiOS version 7.0.10 or above
Please upgrade to FortiOS version 6.4.12 or above
Please upgrade to FortiOS version 6.2.13 or above
Please upgrade to FortiProxy version 7.2.3 or above
Please upgrade to FortiProxy version 7.0.9 or above
Please upgrade to FortiOS-6K7K version 7.0.10 or above
Please upgrade to FortiOS-6K7K version 6.4.12 or above
Please upgrade to FortiOS-6K7K version 6.2.13 or above

 

Workaround for FortiOS:

 

Disable HTTP/HTTPS administrative interface

OR

Limit IP addresses that can reach the administrative interface:

 

config firewall address

edit "my_allowed_addresses"

set subnet <MY IP> <MY SUBNET>

end

 

Then create an Address Group:

 

config firewall addrgrp

edit "MGMT_IPs"

set member "my_allowed_addresses"

end

 

Create the Local in Policy to restrict access only to the predefined group on management interface (here: port1):

 

config firewall local-in-policy

edit 1

set intf port1

set srcaddr "MGMT_IPs"

set dstaddr "all"

set action accept

set service HTTPS HTTP

set schedule "always"

set status enable

next

edit 2

set intf "any"

set srcaddr "all"

set dstaddr "all"

set action deny

set service HTTPS HTTP

set schedule "always"

set status enable

end

 

If using non default ports, create appropriate service object for GUI administrative access:

 

config firewall service custom

edit GUI_HTTPS

set tcp-portrange <admin-sport>

next

edit GUI_HTTP

set tcp-portrange <admin-port>

end

 

Use these objects instead of "HTTPS HTTP "in the local-in policy 1 and 2 below.

 

When using an HA reserved management interface, the local in policy needs to be configured slightly differently - please see: https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-configure-a-local-in-policy-on-a-HA/ta-p/222005

 

Please contact customer support for assistance.

Acknowledgement

Internally discovered and reported by Kai Ni from Burnaby InfoSec team.