Describe the behaviour you want to detect. SARA writes a starting Sigma rule with MITRE tags, false-positive guidance, and detection-engineering context. Anonymous, no account, best-effort generic detection.
title: Potential CVE-2024-21762 FortiOS SSL VPN Exploitation Attempt
id: bb8a7128-ace7-488b-851e-bb9460e2c7b9
date: 2026-08-18
status: experimental
description: >
Detects potential exploitation of CVE-2024-21762, an out-of-bounds write vulnerability
in Fortinet FortiOS SSL VPN. This rule looks for suspicious HTTP requests targeting
the /remote/error endpoint with specific query parameters or anomalous HTTP methods
that match known exploit patterns. This rule is a starting point — tune for your environment.
references:
- https://nvd.nist.gov/vuln/detail/CVE-2024-21762
- https://www.fortiguard.com/psirt/FG-IR-24-015
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: SARA Detection Engineering
tags:
- attack.initial_access
- attack.t1190
logsource:
category: proxy
product: null
detection:
selection_target:
cs-uri-stem|contains|all:
- '/remote/error'
selection_param:
- cs-uri-query|contains: 'errcode='
- cs-method:
- 'PUT'
- 'DELETE'
- 'PATCH'
filter_legit:
cs-user-agent|contains:
- 'FortiClient'
- 'Fortinet'
condition: selection_target and selection_param and not filter_legit
fields:
- c-ip
- cs-method
- cs-uri-stem
- cs-uri-query
- cs-user-agent
- sc-status
falsepositives:
- Legitimate FortiClient or Fortinet management traffic interacting with the error page
- Custom network monitoring or vulnerability scanners checking SSL VPN availability
level: high
Sigma is the open, vendor-neutral format for log-based detections. One rule, written once, converts to Splunk SPL, Elastic ES|QL, KQL for Microsoft Sentinel, Sumo, Chronicle, QRadar, and more. Detection engineers love it for the same reason ATT&CK is the lingua franca for tactics — Sigma is the lingua franca for the queries that detect them.
You've got a fresh write-up of a TTP and need a starting detection in your stack today. Generate, tune, ship.
Pair-program with SARA: the generator produces the skeleton, the engineer learns by tuning, the team commits the result.
You have a rule in one query language; describe it in English and get the Sigma version + conversions to every other backend.
Sketch a detection idea in 30 seconds before investing in a full DE sprint.
SARA Open ships an OpenAI-compatible API. Call POST /api/v1/sigma — Plain English in, valid Sigma YAML out, with MITRE tags and false-positive guidance.
curl -X POST https://sara-open.sirp.io/api/v1/sigma \
-H "Authorization: Bearer $SARA_API_KEY" \
-H "Content-Type: application/json" \
-d '{"description": "PowerShell encoded command from Office"}'
Read the API reference →