---
id: CVE-2026-0300
title: >-
  PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in
  User-ID™ Authentication Portal
summary: >-
  A buffer overflow vulnerability in the User-ID™ Authentication Portal (aka
  Captive Portal) service of Palo Alto Networks PAN-OS software allows an
  unauthenticated attacker to execute arbitrary code with root privileges on the
  PA-Series a…
severity: critical
cvss: 9.3
cvssVector: >-
  CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N/E:A/AU:Y/R:U/V:C/RE:M/U:Red
cvssSource: cna
cwe:
  - CWE-787
vendor: Palo Alto Networks
product: Cloud NGFW
affected:
  - cloud_ngfw
  - PAN-OS >= 12.1.0 < 12.1.7
  - PAN-OS >= 11.2.0 < 11.2.12
  - PAN-OS >= 11.1.0 < 11.1.15
  - PAN-OS >= 10.2.0 < 10.2.18-h6
  - prisma_access
ssvc:
  exploitation: active
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-05-06T00:00:00+00:00'
exploited: true
exploitAvailable: true
published: '2026-05-06'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:11:55.163Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-0300'
references:
  - url: 'https://security.paloaltonetworks.com/CVE-2026-0300'
tags:
  - cve.org
  - in-the-wild
  - exploit-available
  - kev
epss: 0.31725
epssPercentile: 0.98277
kev: true
kevDateAdded: '2026-05-06'
kevDueDate: '2026-05-09'
kevRansomware: false
exploits:
  github: 10
  githubRepos:
    - 'https://github.com/p3Nt3st3r-sTAr/CVE-2026-0300-POC'
    - 'https://github.com/matad0r-maghribi/CVE-2026-0300-PANOS'
    - 'https://github.com/qassam-315/PAN-OS-User-ID-Buffer-Overflow-PoC'
  checkedAt: '2026-10-15T05:53:20.620Z'
zeroDay: true
ingestedAt: '2026-10-15T05:52:46.052Z'
---

## Overview

A buffer overflow vulnerability in the User-ID™ Authentication Portal (aka Captive Portal) service of Palo Alto Networks PAN-OS software allows an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets. 

The risk of this issue is greatly reduced if you secure access to the User-ID™ Authentication Portal per the  best practice guidelines https://knowledgebase.paloaltonetworks.com/KCSArticleDetail  by restricting access to only trusted internal IP addresses.

Prisma Access, Cloud NGFW and Panorama appliances are not impacted by this vulnerability.

## Affected

- `cloud_ngfw`
- `PAN-OS >= 12.1.0 < 12.1.7`
- `PAN-OS >= 11.2.0 < 11.2.12`
- `PAN-OS >= 11.1.0 < 11.1.15`
- `PAN-OS >= 10.2.0 < 10.2.18-h6`
- `prisma_access`

## Remediation

This issue will be fixed in upcoming releases of PAN-OS as captured in the table above.

We strongly recommend that you secure access to your User-ID™ Authentication Portal following the instructions in the workarounds section below.

### Workarounds

Customers can mitigate the risk of this issue by taking either of the following actions:

 * Restrict User-ID™ Authentication Portal access to only trusted zones and in addition, disable Response Pages in the Interface Management Profile attached to every L3 interface in any zone where untrusted/internet traffic can ingress. Keep Response Pages enabled only on interfaces in trust/internal zones where legitimate users' browsers ingress. Refer to Step 6 of the following Live Community article (https://live.paloaltonetworks.com/t5/general-articles/why-it-s-essential-to-secure-your-management-interface/ta-p/1001286) and Knowledgebase article (https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u000000CqbiCAC) for steps to restrict access.
   
 * Disable User-ID™ Authentication Portal if not required.
   

Customers with a Threat Prevention subscription can block attacks for this vulnerability by enabling Threat ID 510019 from Applications and Threats content version 9097-10022. Decoder capabilities necessitate PAN-OS 11.1 or a later version for Threat ID support.