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CVE-2026-0300

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Published May 6, 2026Sources checked Nov 11, 2026
9.8CRITICALCVSS out of 10
What this means

Actively exploited

CISA lists CVE-2026-0300 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Palo Alto Networks PAN-OS.

  • Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Until the vendor releases an official fix, the following workaround should be implemented: - Restrict User-ID Authentication Portal access to only trusted zones. - Disable User-ID Authentication Portal if not required. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.

Public exploit: Not collected.

What to do next

Remediation and response

  • Review the linked vendor advisory and apply the mitigation or fixed release for your affected product.

Palo Alto Networks Security Advisories guidance

Vendor revision: May 28, 2026
Vendor remediation details

VERSION MINOR VERSION SUGGESTED SOLUTION Cloud NGFW No action needed. PAN-OS 12.1 12.1.5 through 12.1.6 Upgrade to 12.1.7 or later. 12.1.2 through 12.1.4-h* Upgrade to 12.1.4-h5 or 12.1.7 or later. PAN-OS 11.2 11.2.11 or later Upgrade to 11.2.12 or later. 11.2.8 through 11.2.10-h* Upgrade to 11.2.10-h6 or 11.2.12 or later. 11.2.5 through 11.2.7-h* Upgrade to 11.2.7-h13 or 11.2.12 or later. 11.2.0 through 11.2.4-h* Upgrade to 11.2.4-h17 or 11.2.12 or later. PAN-OS 11.1 11.1.14 or later Upgrade to 11.1.15 or later. 11.1.11 through 11.1.13-h* Upgrade to 11.1.13-h5 or 11.1.15 or later. 11.1.8 through 11.1.10-h* Upgrade to 11.1.10-h25 or 11.1.15 or later. 11.1.7 through 11.1.7-h* Upgrade to 11.1.7-h6 or 11.1.15 or later. 11.1.5 through 11.1.6-h* Upgrade to 11.1.6-h32 or 11.1.15 or later. 11.1.0 through 11.1.4-h* Upgrade to 11.1.4-h33 or 11.1.15 or later. PAN-OS 10.2 10.2.17 through 10.2.18-h* Upgrade to 10.2.18-h6 or later. 10.2.14 through 10.2.16-h* Upgrade to 10.2.16-h7 or 10.2.18-h6 or later. 10.2.11 through 10.2.13-h* Upgrade to 10.2.13-h21 or 10.2.18-h6 or later. 10.2.8 through 10.2.10-h* Upgrade to 10.2.10-h36 or 10.2.18-h6 or later. 10.2.0 through 10.2.7-h* Upgrade to 10.2.7-h34 or 10.2.18-h6 or later. All older Upgrade to a supported fixed version. unsupported PAN-OS versions Prisma Access No action needed.

Vendor-listed releases

  • Cloud NGFW All
  • PAN-OS 12.1 >= 12.1.4-h5, >= 12.1.7 (ETA: 05/28)
  • PAN-OS 11.2 >= 11.2.4-h17, >= 11.2.7-h13, >= 11.2.10-h6, >= 11.2.12
  • PAN-OS 11.1 >= 11.1.4-h33, >= 11.1.6-h32, >= 11.1.7-h6, >= 11.1.10-h25, >= 11.1.13-h5, >= 11.1.15
  • PAN-OS 10.2 >= 10.2.7-h34, >= 10.2.10-h36, >= 10.2.13-h21, >= 10.2.16-h7, >= 10.2.18-h6
  • Prisma Access All
CISA KEVListedObserved exploitation
EPSS41.7%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview

What is CVE-2026-0300?

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.

Source: NVD

Reported activity

Palo Alto Networks reports limited exploitation of CVE-2026-0300 against PAN-OS User-ID Authentication Portals exposed to untrusted IP addresses or the public internet. Restrict portal access and apply the vendor fix for the installed PAN-OS release.

Palo Alto Networks Security Advisories · Published May 28, 2026
CISA says:Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Until the vendor releases an official fix, the following workaround should be implemented: - Restrict User-ID Authentication Portal access to only trusted zones. - Disable User-ID Authentication Portal if not required. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.CISA catalog due date May 9, 2026