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CVE-2026-0300

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

9.8 CRITICALActively exploited (CISA KEV)EPSS 31.7%
  1. Published6 May 2026
  2. Added to CISA KEV6 May 2026
  3. Remediation due9 May 2026
Actively exploited (CISA KEV)

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.

Added to KEV: 6 May 2026Federal remediation due: 9 May 2026

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Palo Alto Networks PAN-OS10.2.0 · 10.2.1 · 10.2.10 · 10.2.11

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-0300 being actively exploited?

Yes. CVE-2026-0300 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 6 May 2026.

How severe is CVE-2026-0300?

CVE-2026-0300 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 31.7% probability of exploitation.

Which products are affected by CVE-2026-0300?

Affected products include Palo Alto Networks PAN-OS.

How do I fix CVE-2026-0300?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-0300 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.