CVE-2026-0300 — CRITICAL (9.8)

Vulnerability 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.

CVSS Score

9.8

CRITICAL

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

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

HIGH

Integrity

HIGH

Availability

HIGH

Affected Products

Vendor	Product	Versions
Paloaltonetworks	Pan-Os	10.2.0
Paloaltonetworks	Pa-1410	-
Paloaltonetworks	Pa-1420	-
Paloaltonetworks	Pa-3410	-
Paloaltonetworks	Pa-3420	-
Paloaltonetworks	Pa-3430	-
Paloaltonetworks	Pa-3440	-
Paloaltonetworks	Pa-410	-
Paloaltonetworks	Pa-410R	-
Paloaltonetworks	Pa-410R-5G	-
Paloaltonetworks	Pa-415	-
Paloaltonetworks	Pa-415-5G	-
Paloaltonetworks	Pa-440	-
Paloaltonetworks	Pa-445	-
Paloaltonetworks	Pa-450	-
Paloaltonetworks	Pa-450R	-
Paloaltonetworks	Pa-450R-5G	-
Paloaltonetworks	Pa-455	-
Paloaltonetworks	Pa-455-5G	-
Paloaltonetworks	Pa-455R-5G	-

Related Weaknesses (CWE)

CWE-787

References

https://security.paloaltonetworks.com/CVE-2026-0300MitigationVendor Advisory
https://cert-portal.siemens.com/productcert/html/ssa-967325.htmlThird Party Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-US Government Resource

FAQ

What is CVE-2026-0300?

CVE-2026-0300 is a vulnerability with a CVSS score of 9.8 (CRITICAL). 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 wi...

How severe is CVE-2026-0300?

CVE-2026-0300 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.

Is there a patch for CVE-2026-0300?

Check the references section above for vendor advisories and patch information. Affected products include: Paloaltonetworks Pan-Os, Paloaltonetworks Pa-1410, Paloaltonetworks Pa-1420, Paloaltonetworks Pa-3410, Paloaltonetworks Pa-3420.