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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.
This record: live connection— last retrieved: 7 November 2026 at 13:21.
Taken directly from NVD, CISA or the vendor — sometimes in English, unchanged from the source.
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
NETWORK
Privileges required
NONE
User interaction
NONE
Confidentiality
High
Integrity
High
Availability
High
Probability of exploitation within 30 days
41.7%
Percentile
99e
Source: FIRST.org, updated on 6 November 2026.
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.
Our own interpretation and context for the source data above.
IACS Radar assessment
Our own interpretation and context for this vulnerability — not an official source.
IACS Radar priority score
Based on CVSS 9.8, EPSS 41.7%, industrial relevance 35/100; raised due to confirmed active exploitation (KEV) and relevance to internet exposure.
Combines CVSS, EPSS, KEV status, industrial relevance and exposure relevance — a complement to, not a replacement for, the individual scores below and above.
Conditions for exploitation
Operational impact & energy relevance
Possible loss of visibility of or control over the process upon successful exploitation.
No strong energy-sector-specific signals recognised; general OT/ICS relevance.
This product uses protocols that are relevant to internet exposure analysis. An internet-reachable service is not automatically vulnerable.
Recommended defensive measures
Industrial relevance score
Classification is provisional; manual verification by an OT security analyst is recommended.
Classified by IACS Radar-analysepijplijn (geautomatiseerd) on 7 November 2026.
IEC 62443 mapping
Automatic IACS Radar assessment based on the reported CWE weakness classification; not an official certification statement.