Actively exploited
Listed in CISA’s Known Exploited Vulnerabilities catalog since May 6, 2026.
CVE-2026-0300
Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
Added to KEV May 6, 2026
Alert details
- Source feed
- CISA KEV
- CVE ID
- CVE-2026-0300
- CWE
- CWE-787
- Affected products
- PAN-OS · Palo Alto Networks PAN-OS · Palo Alto Networks
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.
What it means for your business
Palo Alto Networks PAN-OS is listed in CISA's Known Exploited Vulnerabilities catalog (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 remediation due date: 2026-05-09. If you need help checking exposure, call (864) 335-9223.
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.
CISA due date: May 9, 2026
Sources
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