Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability (CVE-2026-0300)
Severity: critical · Patch status: unknown · Since 2026-05-06 · 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. CISA added CVE-2026-0300 to its Known Exploited Vulnerabilities catalog on May 6, 2026, which means attackers are exploiting it in the wild.
What to do
- 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.
- US federal agencies must remediate by May 9, 2026 (BOD 22-01); treat that as the outer limit.
Sources
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