CVE-2026-0300

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. Source description excerpt; complete tracked detail loads below.

NVD published: May 6, 2026 · Source record updated: Aug 8, 2026 · Tracker snapshot: Aug 8, 2026

Palo Alto Networks — PAN-OS. Product-level identification only; no affected-version conclusion is available from this field.

NVD published: May 6, 2026 · Source record updated: Aug 8, 2026 · Tracker snapshot: Aug 8, 2026

Act · 468.0

Tracker decision tier from the evidence detailed below · Source record updated: Aug 8, 2026 · Tracker snapshot: Aug 8, 2026

kev-listed · CISA KEV · VulnCheck KEV · ENISA exploited-vulnerability catalog

Active since: May 6, 2026 · CISA KEV added: May 6, 2026 · VulnCheck KEV added: May 5, 2026 · ENISA added: May 6, 2026 · Source record updated: Aug 8, 2026 · Tracker snapshot: Aug 8, 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.

Tracked source remediation field · Source record updated: Aug 8, 2026 · Tracker snapshot: Aug 8, 2026