CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
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.
| Vendor | Palo Alto Networks |
|---|---|
| Product | PAN-OS |
| Date added to KEV | 2026-05-06 |
| Due date (BOD 22-01) | 2026-05-09 |
| Known ransomware campaign use | Unknown |
| CWE | CWE-787 |
| 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. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch. |
What to do
- Identify every instance of Palo Alto Networks PAN-OS in your environment (asset inventory, EDR, vulnerability scanner).
- Apply CISA's 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. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.
- Federal civilian agencies must act by 2026-05-09 under BOD 22-01; other organizations can use the same date as a target.
- Check the vendor advisory and NVD entry linked below for affected versions, then record the fix in your change log.
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Sources
- NVD entry for CVE-2026-0300 (severity scores, if any, live there)
- CISA KEV catalog entry
- https://security.paloaltonetworks.com/CVE-2026-0300
- https://nvd.nist.gov/vuln/detail/CVE-2026-0300