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PAN-OS EUVD-2026-27879

| CVE-2026-0300 CRITICAL
Out-of-bounds Write (CWE-787)
2026-05-06 palo_alto
RCE Buffer Overflow Memory Corruption Paloalto
9.3
CVSS 4.0
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CVSS VectorNVD

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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

5
Patch available
May 06, 2026 - 20:02 EUVD
Analysis Generated
May 06, 2026 - 19:46 vuln.today
CVSS changed
May 06, 2026 - 19:22 NVD
9.3 (CRITICAL)
Added to CISA KEV
May 06, 2026 - 19:18 CISA
CVE Published
May 06, 2026 - 18:57 nvd
CRITICAL 9.3

DescriptionNVD

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.

AnalysisAI

Remote code execution in Palo Alto Networks PAN-OS User-ID Authentication Portal (Captive Portal) allows unauthenticated attackers to execute arbitrary code with root privileges on PA-Series and VM-Series firewalls via specially crafted packets. CISA KEV confirms active exploitation in the wild with publicly available exploit code. …

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RemediationAI

WITHIN 24 HOURS: (1) Identify all PA-Series and VM-Series firewalls in your environment running PAN-OS versions vulnerable to CVE-2026-0300-contact Palo Alto Networks for affected version list if not yet published; (2) restrict network access to the User-ID Captive Portal to trusted internal management networks only via firewall rules or air-gapping; (3) enable enhanced logging and alerting on portal authentication attempts. WITHIN 7 DAYS: (1) review CISA KEV advisories and Palo Alto Networks security bulletins for confirmed vulnerable versions; (2) test failover/backup appliances if portal restriction is not operationally feasible; (3) establish incident response procedures for potential compromise detection. …

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EUVD-2026-27879 vulnerability details – vuln.today
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