Palo Alto Networks PAN-OS Out-of-bounds Write
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.
CISA deadline 2026-05-09 · passed 4 months ago · applies to US federal civilian agencies; used elsewhere as a reference SLA
What happened
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.
Who is affected
Palo Alto Networks PAN-OS. Affected version ranges are listed in the vendor advisory and the NVD entry linked under Sources.
Weakness class: CWE-787.
Timeline
- Added to CISA KEVExploitation in the wild confirmed by CISA
- CISA remediation deadlinepassed 4 months ago
Sources
- NVD entry for CVE-2026-0300 nvd.nist.gov/vuln/detail/CVE-2026-0300
- CISA Known Exploited Vulnerabilities catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
- security.paloaltonetworks.com security.paloaltonetworks.com/CVE-2026-0300
- nvd.nist.gov nvd.nist.gov/vuln/detail/CVE-2026-0300