CVE-2026-0300

PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in User-ID™ Authentication Portal

CRITICAL

9.8

CVSS Score

Published: May 6, 2026 at 06:57 PM UTC

Updated: October 26, 2026 at 07:10 PM UTC

2 products affected across 2 vendorsPAN-OSRUGGEDCOM APE1808 Firmware· also runs on 48 platforms

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Severity

CRITICAL9.8

Exploitation

CISA KEV

Exploit prediction

EPSS 42%

SSVC

Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score41.7%

EPSS (Exploit Prediction Scoring System) estimates a 41.7% chance this CVE is exploited in the wild within the next 30 days — higher than 99% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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.

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.

Ransomware Use

Unknown

Added to KEV

May 6, 2026

Remediation Due

May 9, 2026

176 days overdue

Notes

https://security.paloaltonetworks.com/CVE-2026-0300

https://nvd.nist.gov/vuln/detail/CVE-2026-0300

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

PAN-OS · Palo Alto Networks

95%

10.2.0 10.2.1 10.2.10 10.2.10 h10 10.2.10 h12 10.2.10 h14 10.2.10 h17 10.2.10 h18 10.2.10 h2 10.2.10 h21 10.2.10 h27 10.2.10 h3 10.2.10 h30 10.2.10 h31 10.2.10 h4 10.2.10 h5 10.2.10 h7 10.2.10 h9 10.2.11 10.2.12 10.2.13 10.2.13 h1 10.2.13 h10 10.2.13 h16 10.2.13 h18 10.2.13 h2 10.2.13 h3 10.2.13 h4 10.2.13 h5 10.2.13 h7 10.2.14 10.2.15 10.2.16 10.2.16 h1 10.2.16 h4 10.2.16 h6 10.2.17 10.2.18 10.2.18 h1 10.2.18 h5 10.2.2 10.2.3 10.2.4 10.2.5 10.2.6 10.2.7 10.2.7 h1 10.2.7 h12 10.2.7 h16 10.2.7 h19 10.2.7 h21 10.2.7 h24 10.2.7 h3 10.2.7 h32 10.2.7 h6 10.2.7 h8 10.2.8 10.2.9 11.1.0 11.1.1 11.1.10 11.1.10 h1 11.1.10 h10 11.1.10 h12 11.1.10 h21 11.1.10 h4 11.1.10 h5 11.1.10 h7 11.1.10 h9 11.1.11 11.1.12 11.1.13 11.1.13 h1 11.1.13 h2 11.1.13 h3 11.1.14 11.1.2 11.1.3 11.1.4 11.1.4 h1 11.1.4 h13 11.1.4 h15 11.1.4 h16 11.1.4 h17 11.1.4 h18 11.1.4 h25 11.1.4 h27 11.1.4 h32 11.1.4 h4 11.1.4 h7 11.1.4 h9 11.1.5 11.1.6 11.1.6 h1 11.1.6 h10 11.1.6 h14 11.1.6 h17 11.1.6 h19 11.1.6 h2 11.1.6 h20 11.1.6 h21 11.1.6 h22 11.1.6 h23 11.1.6 h25 11.1.6 h29 11.1.6 h3 11.1.6 h4 11.1.6 h5 11.1.6 h6 11.1.6 h7 11.1.7 11.1.7 h1 11.1.7 h2 11.1.7 h4 11.1.8 11.1.9 11.2.0 11.2.1 11.2.10 11.2.10 h1 11.2.10 h2 11.2.10 h3 11.2.10 h4 11.2.10 h5 11.2.11 11.2.2 11.2.3 11.2.4 11.2.4 h1 11.2.4 h10 11.2.4 h11 11.2.4 h12 11.2.4 h14 11.2.4 h15 11.2.4 h2 11.2.4 h4 11.2.4 h5 11.2.4 h6 11.2.4 h7 11.2.4 h8 11.2.4 h9 11.2.5 11.2.6 11.2.7 11.2.7 h1 11.2.7 h10 11.2.7 h11 11.2.7 h12 11.2.7 h2 11.2.7 h3 11.2.7 h4 11.2.7 h7 11.2.7 h8 11.2.8 11.2.9 12.1.0 12.1.2 12.1.3 12.1.4 12.1.4 h2 12.1.4 h3 12.1.5 12.1.6

Affected range stops below 10.2.18-h6, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.1.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.2.12, so it looks safe — our inference, not a vendor statement

Affected range stops below 12.1.7, so it looks safe — our inference, not a vendor statement

paloaltonetworks-pa-1410 (environment) · paloaltonetworks-pa-1420 (environment) · paloaltonetworks-pa-3410 (environment) · paloaltonetworks-pa-3420 (environment) · paloaltonetworks-pa-3430 (environment) · paloaltonetworks-pa-3440 (environment) · paloaltonetworks-pa-410 (environment) · paloaltonetworks-pa-410r (environment) · paloaltonetworks-pa-410r-5g (environment) · paloaltonetworks-pa-415 (environment) · paloaltonetworks-pa-415-5g (environment) · paloaltonetworks-pa-440 (environment) · paloaltonetworks-pa-445 (environment) · paloaltonetworks-pa-450 (environment) · paloaltonetworks-pa-450r (environment) · paloaltonetworks-pa-450r-5g (environment) · paloaltonetworks-pa-455 (environment) · paloaltonetworks-pa-455-5g (environment) · paloaltonetworks-pa-455r-5g (environment) · paloaltonetworks-pa-460 (environment) · paloaltonetworks-pa-501 (environment) · paloaltonetworks-pa-505 (environment) · paloaltonetworks-pa-510 (environment) · paloaltonetworks-pa-520 (environment) · paloaltonetworks-pa-540 (environment) · paloaltonetworks-pa-5410 (environment) · paloaltonetworks-pa-5420 (environment) · paloaltonetworks-pa-5430 (environment) · paloaltonetworks-pa-5440 (environment) · paloaltonetworks-pa-5445 (environment) · paloaltonetworks-pa-545-poe (environment) · paloaltonetworks-pa-5450 (environment) · paloaltonetworks-pa-550 (environment) · paloaltonetworks-pa-5540 (environment) · paloaltonetworks-pa-555-poe (environment) · paloaltonetworks-pa-5550 (environment) · paloaltonetworks-pa-5560 (environment) · paloaltonetworks-pa-5570 (environment) · paloaltonetworks-pa-5580 (environment) · paloaltonetworks-pa-560 (environment) · paloaltonetworks-pa-7500 (environment) · paloaltonetworks-pa-7500-dpc-a (environment) · paloaltonetworks-vm-100 (environment) · paloaltonetworks-vm-300 (environment) · paloaltonetworks-vm-50 (environment) · paloaltonetworks-vm-500 (environment) · paloaltonetworks-vm-700 (environment)

RUGGEDCOM APE1808 Firmware · Siemens

95%

All versions

siemens-ruggedcom-ape1808 (same device)