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.
- Published May 6, 2026
- CVSS 9.3 critical
- 31.7% chance of exploitation in the next 30 days (EPSS)
- In CISA's Known Exploited Vulnerabilities catalog
Affected software
In the news
- Quantifying 2026 Routinely Targeted Vulnerabilities (So Far) VulnCheck Blog ·
- Critical Vulnerability in PAN-OS CERT-EU ·