CVE-2026-0300

PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in User-ID™ Authentication Portal

State: Published
Severity: 9.3 Critical
Published: May 6, 2026
Updated: Oct 15, 2026
Reserved: Nov 3, 2025

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.

Scores

CVSS	Score	Vector	Source
4.0	9.3 Critical	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	palo_alto
4.0	8.7 High	CVSS:4.0/AV:A/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	palo_alto

Weaknesses

CWE-787 Out-of-bounds Write

Affected Products

Product	Versions
Cloud NGFWPalo Alto Networks	AllNot affected
PAN-OSPalo Alto Networks	12.1.0 to before 12.1.7Affectedfrom 12.1.7Not affectedfrom 12.1.4-h5Not affected 11.2.0 to before 11.2.12Affectedfrom 11.2.12Not affectedfrom 11.2.10-h6Not affectedfrom 11.2.7-h13Not affectedfrom 11.2.4-h17Not affected 11.1.0 to before 11.1.15Affectedfrom 11.1.15Not affectedfrom 11.1.13-h5Not affectedfrom 11.1.10-h25Not affectedfrom 11.1.7-h6Not affectedfrom 11.1.6-h32Not affectedfrom 11.1.4-h33Not affected 10.2.0 to before 10.2.18-h6Affectedfrom 10.2.18-h6Not affectedfrom 10.2.16-h7Not affectedfrom 10.2.13-h21Not affectedfrom 10.2.10-h36Not affectedfrom 10.2.7-h34Not affected
Prisma AccessPalo Alto Networks	AllNot affected

References

https://security.paloaltonetworks.com/CVE-2026-0300vendor-advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300government-resource
https://cert-portal.siemens.com/productcert/html/ssa-967325.html

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