CVE-2026-0300: Palo Alto PAN-OS User-ID Portal Exploitation — Detection and Remediation Guide

---
title: Potential PAN-OS User-ID RCE via Web Service Shell Spawn
id: 8a4b2c91-1d3e-4f5a-a9b6-7c8d9e0f1a2b
status: experimental
description: Detects potential RCE on PAN-OS devices by identifying the web server process spawning a shell. This is a common post-exploitation behavior for buffer overflows in web services.
references:
  - https://securityadvisories.paloaltonetworks.com/
author: Security Arsenal
date: 2026/05/12
tags:
  - attack.initial_access
  - attack.execution
  - cve.2026.0300
logsource:
  category: process_creation
  product: linux
detection:
  selection:
    ParentImage|endswith:
      - '/lighttpd'
      - '/nginx'
      - '/pan_task'
    Image|endswith:
      - '/sh'
      - '/bash'
      - '/dash'
  condition: selection
falsepositives:
  - Legitimate administrative debugging (rare)
level: critical
---
title: PAN-OS Buffer Overflow Heuristic - Anomalous URI Length
id: 9b5c3d02-2e4f-5g6b-b0c7-8d9e1f2a3b4c
status: experimental
description: Detects potential buffer overflow attempts against the User-ID portal by identifying unusually long URI query parameters or headers in web logs.
references:
  - https://thehackernews.com/2026/05/palo-alto-pan-os-flaw-under-active.html
author: Security Arsenal
date: 2026/05/12
tags:
  - attack.initial_access
  - cve.2026.0300
logsource:
  category: webserver
  product: pan-os
detection:
  selection_target:
    cs_uri_stem|contains: '/user-id'
  selection_overflow:
    cs_uri_query|length: > 500
  condition: all of selection_*
falsepositives:
  - Misconfigured legacy clients
level: high


**KQL (Microsoft Sentinel / Defender)**

// Hunt for potential CVE-2026-0300 exploitation indicators in PAN-OS Traffic Logs
// Focus on User-ID portal access with suspicious characteristics
CommonSecurityLog
| where DeviceVendor == "Palo Alto Networks"
| where RequestURL contains "/user-id" 
| extend UriLength = strlen(RequestURL)
| where UriLength > 1000 or SentBytes > 2000
| project TimeGenerated, DeviceName, SourceIP, DestinationIP, RequestURL, SentBytes, ReceivedBytes, Activity
| order by TimeGenerated desc
| extend Reason = "Potential Buffer Overflow Attempt detected via URI length"


**Velociraptor VQL**

-- Hunt for suspicious network connections indicative of PAN-OS management access
-- or established reverse shells from the firewall appliance
SELECT *
FROM listen_sockets()
WHERE Family = "inet"
  AND (Port = 443 OR Port = 4443 OR Port = 22)
  AND State != "LISTEN"
  AND Pid IN (
    SELECT Pid FROM pslist() 
    WHERE Name =~ "lighttpd" OR Name =~ "pan_agent"
  )


**Remediation Script (Bash)**

#!/bin/bash
# CVE-2026-0300 Remediation Verification Script
# This script checks if the PAN-OS User-ID service is listening on untrusted interfaces.
# Note: Actual patching requires the CLI or Panorama.

echo "[+] Checking for User-ID Service Exposure..."

# Check if User-ID process is running
if pgrep -f "user-id" > /dev/null; then
    echo "[WARNING] User-ID process is active."
    
    # Check listening sockets for User-ID port (default 443 or custom)
    # This looks for the service listening on non-loopback addresses
    netstat -tulpen | grep ":443 " | grep -v "127.0.0.1" | while read -r line; do
        echo "[ALERT] Potential Exposure Detected: $line"
    done
else
    echo "[INFO] User-ID process not detected running."
fi

echo "[!] REMEDIATION STEPS:"
echo "1. Immediate: Disable User-ID Authentication Portal on all Untrust zones via CLI:"
echo "   set management user-id-authentication <zone> disable"
echo "2. Apply the relevant hotfix for CVE-2026-0300 immediately."
echo "3. Review logs for signs of exploitation in the last 30 days."

Update to the fixed PAN-OS versions immediately. Refer to the official Palo Alto Networks Security Advisory for CVE-2026-0300 for the exact minor versions for your specific release train.