CVE-2026-0300
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.
Summary dbcve.org
A buffer overflow vulnerability exists in the User-ID Authentication Portal (Captive Portal) service of PAN-OS software. An unauthenticated attacker can send specially crafted packets to trigger the overflow and achieve arbitrary code execution with root privileges on affected PA-Series and VM-Series firewalls.
Mitigation
Apply the vendor patch when available and immediately implement network access controls to restrict Captive Portal access to trusted internal IP addresses only, per Palo Alto best practices.