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Vulnerabilities

Vulnerability · CVE-2026-0300

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

Published May 5, 2026 · catalog updated Jun 17, 2026 · Palo Alto Networks PAN-OS

Patch now

CVE-2026-0300 is in the CISA known-exploited catalog, due May 9, 2026. Confirm Palo Alto Networks PAN-OS against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
Critical9.3
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
31.72%
Remediation
Remediation guidance
Affected products
cpe paloaltonetworks/pan-os · cpe siemens/ruggedcom ape1808 firmware · vendor 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • 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

How to fix CVE-2026-0300

  • Recommended remediation

    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.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2026-0300 is in the CISA known-exploited catalog, due May 9, 2026. Confirm Palo Alto Networks PAN-OS against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with 10.2.0, 10.2.1, 10.2.2, 10.2.3, 10.2.4, 10.2.5. 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.

What should an analyst verify?

CWE-787: Out-of-bounds Write. EPSS 31.72%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

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

  5. Jun 17, 2026 · NIST NVD

    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

Sources

  • CISA KEVConfirmed exploitationCVE-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.orgVulnerability recordCVE-2026-0300

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-0300

    30-day exploitation probability 31.7%

    first.org
  • NIST NVDVulnerability recordCVE-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
  • VulnCheck KEVConfirmed exploitationCVE-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

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.