CVE-2026-0300
critical CISA KEVPalo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
Vendor / product: Palo Alto Networks — PAN-OS
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Required action (CISA)
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.
Affected products
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
References
- https://security.paloaltonetworks.com/CVE-2026-0300 psirt@paloaltonetworks.com
- https://cert-portal.siemens.com/productcert/html/ssa-967325.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300 134c704f-9b21-4f2e-91b3-4a467353bcc0