Detection: Fortinet Appliance Auth bypass

Updated Date: 2024-05-12 ID: a83122f2-fa09-4868-a230-544dbc54bc1c Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects attempts to exploit CVE-2022-40684, a Fortinet appliance authentication bypass vulnerability. It identifies REST API requests to the /api/v2/ endpoint using various HTTP methods (GET, POST, PUT, DELETE) that may indicate unauthorized modifications, such as adding SSH keys or creating new users. This detection leverages the Web datamodel to monitor specific URL patterns and HTTP methods. This activity is significant as it can lead to unauthorized access and control over the appliance. If confirmed malicious, attackers could gain persistent access, reroute network traffic, or capture sensitive information.

Search

1
2| tstats count min(_time) as firstTime max(_time) as lastTime from datamodel=Web where Web.url IN ("*/api/v2/cmdb/system/admin*")  Web.http_method IN ("GET", "PUT") by Web.http_user_agent, Web.http_method, Web.url, Web.url_length, Web.src, Web.dest, sourcetype 
3| `drop_dm_object_name("Web")` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `fortinet_appliance_auth_bypass_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Palo Alto Network Threat	Network	`'pan:threat'`	`'pan:threat'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
fortinet_appliance_auth_bypass_filter	`search *`

fortinet_appliance_auth_bypass_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1190	Exploit Public-Facing Application	Initial Access
T1133	External Remote Services	Initial Access

KillChainPhase.DELIVERY

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_13

APT28

APT29

APT39

APT41

APT5

Axiom

BackdoorDiplomacy

BlackTech

Blue Mockingbird

Cinnamon Tempest

Dragonfly

Earth Lusca

FIN13

FIN7

Fox Kitten

GALLIUM

GOLD SOUTHFIELD

HAFNIUM

Ke3chang

Kimsuky

Magic Hound

Moses Staff

MuddyWater

Rocke

Sandworm Team

Threat Group-3390

ToddyCat

Volatile Cedar

Volt Typhoon

menuPass

APT18

APT28

APT29

APT41

Akira

Chimera

Dragonfly

FIN13

FIN5

GALLIUM

GOLD SOUTHFIELD

Ke3chang

Kimsuky

LAPSUS$

Leviathan

OilRig

Sandworm Team

Scattered Spider

TeamTNT

Threat Group-3390

Wizard Spider

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

This detection requires the Web datamodel to be populated from a supported Technology Add-On like Splunk for Apache. Splunk for Nginx, or Splunk for Palo Alto.

Known False Positives

GET requests will be noisy and need to be filtered out or removed from the query based on volume. Restrict analytic to known publically facing Fortigates, or run analytic as a Hunt until properly tuned. It is also possible the user agent may be filtered on Report Runner or Node.js only for the exploit, however, it is unknown at this if other user agents may be used.

Associated Analytic Story

CVE-2022-40684 Fortinet Appliance Auth bypass

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Potential CVE-2022-40684 against a Fortinet appliance may be occurring against $dest$.	81	90	90

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`pan:threat`	`pan:threat`
Integration	✅ Passing	Dataset	`pan:threat`	`pan:threat`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 2