CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Required action (CISA's text)

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.

Description (NVD)

Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability in the User-ID Authentication Portal (aka Captive Portal) service that can allow an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets.

SOURCES

• CISA KEVCISA Known Exploited Vulnerabilities catalog

Other Palo Alto Networks flaws

• CVE-2026-0322: Palo Alto Networks PAN-OS Code Injection Vulnerability
• CVE-2026-0257: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
• CVE-2025-0111: Palo Alto Networks PAN-OS File Read Vulnerability
• CVE-2025-0108: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
• CVE-2024-3393: Palo Alto Networks PAN-OS Malicious DNS Packet Vulnerability

Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.