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emorlang_FTNT
Staff
emorlang_FTNT
Staff
February 4, 2026

Technical Tip: Using FortiAnalyzer to detect activities related to the Versa Concerto SD-WAN Authentication Bypass | CVE-2025-34026

  • February 4, 2026
  • 0 replies
  • 155 views
Description

This article describes how to use a custom event handler in FortiAnalyzer to raise alerts for incident response related to attacks that attempt to leverage the Versa Concerto SD-WAN Authentication Bypass. A report is also provided to gain historical visibility into the logs.

 

Note that this article provides alpha files which are automatically generated. The article will be continually updated as more information becomes available.

 

For more information about this attack, see the following FortiGuard Outbreak Alert:

Versa Concerto SD-WAN Authentication Bypass.
Scope

This article contains the files necessary to load an event handler and report into the FortiAnalyzer for either a Fabric ADOM or a FortiGate ADOM. The Fabric report and event handler leverage logs from other Fortinet products that can be used to detect the attack in addition to FortiGate logs.
Solution

What is included in Fortinet_Versa Concerto SD-WAN Authentication Bypass.zip:

  1. Versa Concerto SD-WAN Authentication Bypass_event-handler.json: This event handler helps identify Versa Concerto SD-WAN Authentication Bypass attacks detected by FortiGate and other Fortinet products. This event handler is configured for Fabric ADOMs.
  2. Versa Concerto SD-WAN Authentication Bypass_report.dat: This report displays the findings on Versa Concerto SD-WAN Authentication Bypass from FortiGate and other Fortinet products. It is configured for Fabric ADOMs.
  3. fgt_Versa Concerto SD-WAN Authentication Bypass_event-handler.json: The event handler for FortiGate ADOMs is configured for FortiGate logs only.
  4. fgt_Versa Concerto SD-WAN Authentication Bypass_report.dat: The FortiGate ADOMs report includes only FortiGate charts.

 

Steps:

  1. Download the Fortinet_Versa Concerto SD-WAN Authentication Bypass.zip file (contains 4 files).
  2. Unzip Fortinet_Versa Concerto SD-WAN Authentication Bypass.zip.
  3. Import Versa Concerto SD-WAN Authentication Bypass_event-handler.json or fgt_Versa Concerto SD-WAN Authentication Bypass_event-handler.json event handler:
  • Choose an ADOM (if ADOMs are enabled). The ADOM may have the Fabric or FortiGate type.
  • Choose the FortiSOC module. 
  • Select Event Handler List.
  • Select the Import option under More.
  • Select the appropriate event handler depending on the ADOM type.
emorlang_FTNT_0-1770158046773.png

 

Result:

The event handler is enabled and will be triggered if the appropriate logs are received following the import of the event handler. 

Edit the event handler to customize the notification section.

 

Import Versa Concerto SD-WAN Authentication Bypass_report.dat or fgt_Versa Concerto SD-WAN Authentication Bypass_report.dat to Reports:

  • Choose an ADOM (if ADOMs are enabled). The ADOM may have the Fabric or FortiGate type.
  • Choose the Report module.
  • Select the Import option under 'More'.
  • Select the appropriate file for the ADOM type to add the report to the ADOM.
emorlang_FTNT_1-1770158046773.png

 

Result: 

The Versa Concerto SD-WAN Authentication Bypass_report can be run anytime as determined by an admin user.
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