Fortinet Patches Critical FortiSIEM Path Traversal
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Fortinet fixed a critical unauthenticated path traversal flaw (CVSS 9.8) in FortiSIEM 7.5.0 enabling remote code execution.
NCSC-NL published an advisory covering two vulnerabilities patched by Fortinet in FortiSIEM version 7.5.0. The first and most severe, CVE-2026-106173 (CVSS 9.8), is a path traversal issue stemming from insufficient restriction of pathnames to restricted directories. An unauthenticated attacker can send specially crafted packets to execute unauthorized code or commands, posing a critical remote compromise risk.
The second issue, CVE-2026-106176 (CVSS 3.8), is a missing authorization check within the GUI component. An authenticated attacker can send specially crafted HTTP requests to bypass authorization controls and similarly execute unauthorized code or commands, though this requires existing access and has lower impact.
Both vulnerabilities can lead to unauthorized command execution and compromise of system integrity and security. Fortinet has released updates addressing both issues. No in-the-wild exploitation is mentioned in the advisory. Defenders running FortiSIEM should prioritize patching to the fixed version immediately given the unauthenticated, pre-auth nature of the critical flaw, and review GUI access logs for anomalous authenticated requests as a secondary measure.
Mentioned in this report
Detection guidance
Web Request with Encoded or Repeated Path Traversal Sequences Returning Success
Detects HTTP requests with repeated or URL-encoded directory traversal sequences that receive a 200 response, the generic pattern of path-traversal exploitation such as the FortiSIEM flaw. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Web Request with Encoded or Repeated Path Traversal Sequences Returning Success
description: Detects web requests whose URI or query contains repeated or URL-encoded
directory traversal sequences and that return HTTP 200. The advisory describes an
unauthenticated path traversal (CVE-2026-106173) in FortiSIEM that leads to command
execution. The report gives no endpoint, so this rule matches the generic traversal
technique and should be scoped to FortiSIEM and other management-plane web servers.
tags:
- attack.privilege-escalation
- attack.t1068
- attack.initial-access
- attack.t1190
logsource:
category: webserver
detection:
selection_uri:
cs-uri-stem|contains:
- ../../
- ..%2f..%2f
- '%2e%2e%2f%2e%2e%2f'
- '%2e%2e/%2e%2e/'
- ..%5c..%5c
- '%252e%252e%252f'
cs-uri-query|contains:
- ../../
- ..%2f..%2f
- '%2e%2e%2f%2e%2e%2f'
- '%2e%2e/%2e%2e/'
- ..%5c..%5c
- '%252e%252e%252f'
selection_status:
sc-status: 200
condition: 1 of selection_uri and selection_status
falsepositives:
- Vulnerability scanners run by the security team against internal web servers
- Applications that pass relative file paths as URL parameters
level: medium
id: c8a28555-0225-586c-98d9-01991758c25c
status: experimental
author: Vorant
references:
- https://advisories.ncsc.nl/2026/ncsc-2026-0434.html
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://advisories.ncsc.nl/2026/ncsc-2026-0434.html
What this brief leaves out
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