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CVE-2026-0300

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

Palo Alto Networks · CWE-787 — Out-of-bounds write · in CISA KEV since 2026-05-06

CISA federal deadline · Overdue by 5 monthsCISA KEVActively Exploited
75

EVRS 75 of 100 Urgent

Patch This Cycle

Rank 819 of 2,955 tracked

Raised to the floor for a confirmed exploited vulnerability.

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Why it scores 75

Evidence available: 6 of 7 signals

Listed in the CISA KEV catalog, and an EPSS probability of 0.317.

  • CISA KEVApplied
  • RansomwareDid not apply
  • Vendor exploitationDid not apply
  • EPSSApplied
  • Microsoft Exploitability IndexNot applicable
  • Pre-patch disclosureNo data
  • KEV recencyDid not apply
  • CVSSApplied

The band answers “how soon”, not “how bad”. No data for: Pre-patch disclosure. Why some signals show no data

Fix

No fixed version identified yet

CISA required action

Affected versions

  • pan-os10.2.010.2.110.2.210.2.310.2.410.2.510.2.610.2.710.2.810.2.910.2.1010.2.1110.2.1210.2.1310.2.1410.2.1510.2.1610.2.1710.2.1811.1.011.1.111.1.211.1.311.1.411.1.511.1.611.1.711.1.811.1.911.1.1011.1.1111.1.1211.1.1311.1.1411.2.011.2.111.2.211.2.311.2.411.2.511.2.611.2.711.2.811.2.911.2.1011.2.1112.1.212.1.312.1.412.1.512.1.6
  • ruggedcom ape1808 firmware
  • pa-1410
  • pa-1420
  • pa-3410
  • pa-3420
  • pa-3430
  • pa-3440

+42 more affected products; see the full list at NVD.

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.

Evidence

Each value with its source
MeasureValueSource
CVSS base scoreHow severe the flaw is in itself. It does not say how likely an attack is. 9.3 NVD
FIRST EPSSFIRST's estimate of the chance this is exploited in the next 30 days, and how that ranks against all CVEs. 0.317 (98.3rd pctl) FIRST EPSS
Actively exploitedWhether a source of record has confirmed attacks using it in the wild. Confirmed CISA KEV
Ransomware campaign useWhether CISA has seen ransomware operators use it. Unknown or none CISA KEV
CISA remediation deadlineThe date US federal agencies must have fixed or mitigated it. 2026-05-09 · CISA federal deadline · Overdue by 5 months CISA KEV
Public exploit moduleA module existing is not the same as active exploitation. None known Metasploit
EUVD cross-referenceENISA's record: CVSS 9.3 (v4.0), assigned by palo_alto. Listed ENISA EUVD

Description

NVD

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.

What CISA says to do