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CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Palo Alto Networks PAN-OS · in CISA KEV since 2026-05-06

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2026-05-06added to KEV

2026-05-09federal remediation due date

31.72%EPSS exploit probability (30 days) 98.2th percentile

9.3 CRITICALCVSS 4.0

Unknownknown ransomware use

0days from NVD publication to KEV

What it is

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.

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.

CWE	CWE-787
CVSS vector	`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N/E:A/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:C/RE:M/U:Red`
NVD published	2026-05-06 (Analyzed)

Original records: NVD · CISA KEV · JSON: /api/cve/CVE-2026-0300.json · all KEV CVEs

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