CVE-2026-0300

CriticalCVSS 9.8/10Known exploited (CISA KEV)Last modified Jun 17, 2026

Description

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.

Metrics

CVSS 3.1 9.8/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-787

Affected software

No affected versions have been published.

Timeline

Published
May 6, 2026
Last modified
Jun 17, 2026
Added to CISA KEV
May 6, 2026
NVD status
Analyzed

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CVE-2026-0300: Critical severity, CVSS 9.8 | Vulnix