Exploited CVEs / Palo Alto Networks / CVE-2026-0300

CVE-2026-0300

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2026-05-09 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Palo Alto Networks Security Advisories, linked below.

Risk summary

CriticalCISA KEV
9.8
CVSS base
32%
EPSS exploit probability
Critical
Severity
2026-05-06
Added to KEV
2026-05-09 (past due)
CISA due date

Actively exploited Palo Alto Networks PAN-OS vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2026-05-06.

Senserva AI read on CVE-2026-0300CISA required actionOfficial fix for CVE-2026-0300What the press saysAdmin questions

Senserva AI Opinion for CVE-2026-0300

An out-of-bounds write in the PAN-OS User-ID Authentication Portal, also known as Captive Portal, lets an unauthenticated attacker execute code as root on PA-Series and VM-Series firewalls. It is Critical at CVSS 9.8 with a 36% EPSS score, and exploitation was confirmed on 2026-05-06. Only firewalls with the Captive Portal service enabled expose the vulnerable path, which narrows the target set but makes those devices urgent.

Do this: Identify firewalls running Captive Portal, patch them first, and disable the portal where it is not actually needed.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-0300

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

Patch now
Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.
The fix ships from the vendor: Palo Alto Networks Security Advisories.
Do this now: Federal remediation deadline 2026-05-09; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 15, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2026-0300

Published
2026-05-06
Last revised
2026-05-06
Changes tracked
1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one
What changed, and when
  • 2026-05-06 added to the CISA KEV catalog by CISA
  • 2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 32.1%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2026-05-09 (past 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 Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.

Official fix for CVE-2026-0300

The authoritative fix and affected-version list are published by the vendor. Find the PAN-OS advisory on Palo Alto Networks Security Advisories.

Palo Alto Networks Security AdvisoriesCISA KEV entry

Common questions about CVE-2026-0300

Is CVE-2026-0300 actively exploited?

Yes. CVE-2026-0300 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-05-06, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 32%.

What is the CISA deadline and required action for CVE-2026-0300?

CISA set the federal (BOD 22-01) remediation due date at 2026-05-09, which has passed; treat any unremediated system as overdue. The verbatim 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.

What fixes CVE-2026-0300?

The authoritative fix is in the vendor advisory: see Palo Alto Networks Security Advisories for the patched PAN-OS versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2026-0300?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2026-0300's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited Palo Alto Networks CVEs
CVE-2026-0257CVE-2025-0111CVE-2025-0108CVE-2024-3393CVE-2024-0012CVE-2024-9474CVE-2024-9465CVE-2024-9463

All Palo Alto Networks exploited CVEs on one page: Palo Alto Networks vulnerabilities actively exploited.

Authoritative references
CVE recordNVD detailCISA KEV catalogFIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
Provided as is, without warranty; verify against the vendor advisory before acting. Data notice and terms.