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

Added to the CISA Known Exploited Vulnerabilities catalog on 06 May 2026. Vendor: Palo Alto Networks. Product: PAN-OS.

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.

Required action: 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. (due 09 May 2026)