CVE-2026-0300

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 4.0

9.3CVSS: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

CVSS 3.1

9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

42% chance of exploitation in the next 30 days; higher than 98% of CVEs (scores of 2026-10-26)

CISA KEV

listed 2026-05-06, due 2026-05-09

CWE

CWE-787

Published

2026-05-06

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• paloaltonetworks:pan-os
• siemens:ruggedcom_ape1808_firmware

References

• https://security.paloaltonetworks.com/CVE-2026-0300
• https://cert-portal.siemens.com/productcert/html/ssa-967325.html
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300

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