Critical 9.3Known exploited (CISA KEV)Published May 6, 2026

CVE-2026-0300PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in User-ID™ Authentication Portal

Updated under an hour ago (Oct 26, 2026, 7:10 PM ET)

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It affects Palo Alto Networks Cloud NGFW and 5 other products. Add what you run to find out whether that includes you.

CISA lists it as known exploited since May 6, 2026; federal agencies had to remediate by May 9, 2026. Treat that date as your deadline.

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Every CVE for Palo Alto Networks Cloud NGFW

Exploited in the last 30 days

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: 9.3 CRITICAL (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N/E:A/AU:Y/R:U/V:C/RE:M/U:Red
Weakness (CWE): CWE-787
Known exploited: Added to CISA KEV May 6, 2026; federal remediation due May 9, 2026Apply 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.
EPSS (exploitation in the next 30 days): 41.71% (percentile 99)
Assigned by: palo_alto
NVD analysis: Analyzed
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Palo Alto Networks Cloud NGFW palo_alto_networks:cloud_ngfw (from the name)	all versions not affected	CNA record
Palo Alto Networks PAN-OS palo_alto_networks:pan-os	from 12.1.0 before 12.1.7; fixed at 12.1.7, fixed at 12.1.4-h5; from 11.2.0 before 11.2.12; fixed at 11.2.12, fixed at 11.2.10-h6, fixed at 11.2.7-h13, fixed at 11.2.4-h17; from 11.1.0 before 11.1.15; fixed at 11.1.15, fixed at 11.1.13-h5, fixed at 11.1.10-h25, fixed at 11.1.7-h6, fixed at 11.1.6-h32, fixed at 11.1.4-h33; from 10.2.0 before 10.2.18-h6; fixed at 10.2.18-h6, fixed at 10.2.16-h7, fixed at 10.2.13-h21, fixed at 10.2.10-h36, fixed at 10.2.7-h34	CNA record
Palo Alto Networks Prisma Access palo_alto_networks:prisma_access (from the name)	all versions not affected	CNA record
Siemens RUGGEDCOM APE1808 siemens:ruggedcom_ape1808 (from the name)	all versions	CISA ADP
paloaltonetworks pan-os paloaltonetworks:pan-os	10.2.0; 10.2.1; 10.2.2; 10.2.3; 10.2.4; 10.2.5; 10.2.6; 10.2.7; and 154 more ranges	NVD
siemens ruggedcom_ape1808_firmware siemens:ruggedcom_ape1808_firmware	all versions	NVD

References

References

https://security.paloaltonetworks.com/CVE-2026-0300	vendor-advisory, mitigation
https://cert-portal.siemens.com/productcert/html/ssa-967325.html	third-party-advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300	us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.