CVE-2025-68686: Fortinet FortiOS Symlink Bypass — Detection and Remediation

---
title: FortiOS Potential Symlink Bypass via Suspicious HTTP Requests
id: 8f2c4a10-d1e9-4a5f-b9c2-1a3b4c5d6e7f
status: experimental
description: Detects potential exploitation attempts of CVE-2025-68686 by identifying suspicious URI patterns in FortiOS logs that may indicate symlink bypass attempts via crafted HTTP requests.
references:
 - https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal
date: 2026/07/28
tags:
 - attack.initial_access
 - attack.t1190
 - attack.defense_evasion
 - attack.t1074
logsource:
 category: webserver
 product: fortinet
detection:
 selection:
   cfp|startswith: 'FGT'
   request|contains:
     - '../'
     - '%2e%2e%2f'
     - '....//'
   http_method|contains:
     - 'GET'
     - 'POST'
 condition: selection
falsepositives:
 - Scanning activity or misconfigured web clients
level: high
---
title: FortiOS Sensitive File Access via HTTP
id: 9g3d5b20-e2f0-5b6g-c0d3-2b4c5d6e7f0g
status: experimental
description: Detects attempts to access sensitive system files or configuration directories via the web interface, a common indicator of information disclosure vulnerabilities.
references:
 - https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal
date: 2026/07/28
tags:
 - attack.collection
 - attack.t1005
logsource:
 category: webserver
 product: fortinet
detection:
 selection:
   cfp|startswith: 'FGT'
   uri|contains:
     - '/etc/'
     - '/dev/'
     - '/var/log/'
     - 'api/v2/monitor/system'
 condition: selection
falsepositives:
 - Authorized administrative access
level: medium

// Hunt for suspicious HTTP patterns indicative of CVE-2025-68686 bypass attempts
// leveraging CommonSecurityLog for Fortinet devices
CommonSecurityLog
| where DeviceVendor == "Fortinet"
| where ExtID has "FGT" // Filter for FortiGate devices
| where RequestMethod in ("GET", "POST")
| where RequestURL has @"../" 
   or RequestURL has @"%2e%2e" 
   or RequestURL has @"/etc/" 
   or RequestURL has @"/dev/"
| project TimeGenerated, DeviceName, SourceIP, DestinationIP, RequestURL, RequestMethod, ExtID
| sort by TimeGenerated desc

-- Hunt for evidence of symlink creation or suspicious file access
-- on Linux-based endpoints (if FortiOS debugging/shell access is available during IR)
SELECT 
  FullPath, 
  Size, 
  Mode.String AS Perms,
  Mtime,
  Atime
FROM glob(globs="/**/*")
WHERE Mode.String =~ "^l" 
  AND FullPath =~ "/var/log/|/etc/|/data/"
-- Look for recently modified symlinks in system directories
  AND (Mtime > now() - 7d)

#!/bin/bash
# FortiOS CVE-2025-68686 Remediation Verification Script
# This script checks the FortiOS version against the vulnerable list.
# Note: Actual patching must be done via the FortiOS GUI or CLI.

# Define vulnerable versions (Example placeholder - replace with actual advisory data)
VULNERABLE_VERSIONS=("7.2.0" "7.2.1" "7.0.0")
TARGET_IP="192.168.1.1" # Replace with your FortiGate IP
API_TOKEN="YOUR_API_TOKEN" # Replace with a restricted API Token

# Check current version using FortiOS API
echo "Checking FortiOS version for $TARGET_IP..."
CURRENT_VERSION=$(curl -s -k "https://$TARGET_IP/api/v2/cmdb/system/global?access_token=$API_TOKEN" | jq -r '.results[0]."fos-version"')

if [ -z "$CURRENT_VERSION" ]; then
  echo "Error: Could not retrieve version. Check API connectivity and Token."
  exit 1
fi

echo "Current FortiOS Version: $CURRENT_VERSION"

# Check against vulnerable list (Simple string match for demo)
for ver in "${VULNERABLE_VERSIONS[@]}"; do
  if [[ "$CURRENT_VERSION" == "$ver"* ]]; then
    echo "[ALERT] System is running a vulnerable version: $CURRENT_VERSION"
    echo "Action Required: Apply the latest security patches from Fortinet immediately."
    exit 1
  fi
done

echo "[OK] Version $CURRENT_VERSION does not match known vulnerable baseline."
echo "Please verify specific patch build numbers in the Fortinet PSIC Advisory."