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Findings

CVE-2026-0300

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Published May 6, 2026 · updated Jun 17, 2026 · Palo Alto Networks PAN-OS

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.

Timeline

Detection, updates, and resolution for this record.

  1. May 6, 2026 · Catalog

    Detected

    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 p

  2. May 6, 2026 · CISA KEV

    Known exploited

    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

  3. May 9, 2026 · CISA KEV

    Remediation due

    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

  4. Jun 17, 2026 · Catalog

    Updated

    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 p

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

Affected

  • cpe paloaltonetworks/pan-os10.2.0
  • cpe paloaltonetworks/pan-os10.2.1
  • cpe paloaltonetworks/pan-os10.2.2
  • cpe paloaltonetworks/pan-os10.2.3
  • cpe paloaltonetworks/pan-os10.2.4
  • cpe paloaltonetworks/pan-os10.2.5
  • cpe paloaltonetworks/pan-os10.2.6
  • cpe paloaltonetworks/pan-os10.2.7
  • cpe siemens/ruggedcom ape1808 firmwareversion unspecified
  • vendor Palo Alto Networks PAN-OSversion unspecified

Sources

  • CISA KEVCVE-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.gov
  • CVE.orgCVE-2026-0300

    Official CVE identifier

    cve.org
  • FIRST EPSSCVE-2026-0300

    30-day exploitation probability 31.7%

    first.org
  • NIST NVDCVE-2026-0300

    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

    nvd.nist.gov

References