Detection rules › Sigma
Fortinet CVE-2021-22123 Exploitation
Detects CVE-2021-22123 exploitation attempt against Fortinet WAFs
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access |
Rule body
title: Fortinet CVE-2021-22123 Exploitation
id: f425637f-891c-4191-a6c4-3bb1b70513b4
status: test
description: Detects CVE-2021-22123 exploitation attempt against Fortinet WAFs
references:
- https://www.rapid7.com/blog/post/2021/08/17/fortinet-fortiweb-os-command-injection
author: Bhabesh Raj, Florian Roth
date: 2021-08-19
modified: 2023-01-02
tags:
- attack.initial-access
- attack.t1190
- cve.2021-22123
- detection.emerging-threats
logsource:
category: webserver
detection:
selection:
cs-uri-query|contains: '/api/v2.0/user/remoteserver.saml'
cs-method: POST
filter1:
cs-referer|contains: '/root/user/remote-user/saml-user/'
filter2:
cs-referer: null
condition: selection and not filter1 and not filter2
falsepositives:
- Unknown
level: critical
Stages and Predicates
Stage 0: condition
selection and not filter1 and not filter2Stage 1: selection
selection:
cs-uri-query|contains: '/api/v2.0/user/remoteserver.saml'
cs-method: POST
Stage 2: not filter1
filter1:
cs-referer|contains: '/root/user/remote-user/saml-user/'
Stage 3: not filter2
filter2:
cs-referer: null
Exclusions
The rule actively suppresses these predicates.
| Field | Kind | Excluded values | Search |
|---|---|---|---|
cs-referer | match | /root/user/remote-user/saml-user/ | excludes:cs-referer field:"cs-referer" value:"/root/user/remote-user/saml-user/" |
cs-referer | is_null | excludes:cs-referer |
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
cs-method | eq |
| field:"cs-method" kind:eq value:"POST" |
cs-uri-query | match |
| field:"cs-uri-query" kind:match value:"/api/v2.0/user/remoteserver.saml" |