Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
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
What happened
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.
CISA lists it as exploited, added 06 May 2026.
Does it affect you
Names Palo Alto Networks PAN-OS. Enter the product and version you run to place it against the affected range the vendor published.
What to do
- Follow the vendor advisory for the fixed release and any interim mitigation.
security.paloaltonetworks.com - 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.
cisa.gov
CISA’s notes for this entry:
Affected, as published to NVD
- panos
- Palo Alto Networks PAN-OS: exactly 10.2.0
The record
- NVD status
- Analyzed
- Published
- 06 May 2026, last modified 17 Jun 2026 (NVD)
- Severity
- CVSS 3.1 base score 9.8, Critical — computed here from the vector; NVD states 9.8.
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness
- CWE-787 Out-of-bounds Write (NVD; names by MITRE)
- Exploitation
- Listed in CISA’s Known Exploited Vulnerabilities catalogue since 06 May 2026; federal remediation due 09 May 2026. CISA entry
- Exploit probability
- EPSS 31.7%, 98th percentile — FIRST, scored 23 Oct 2026. FIRST EPSS
- Vendor
- Palo Alto Networks · PAN-OS (CISA)
References on the NVD record
- security.paloaltonetworks.com/CVE-2026-0300MitigationVendor Advisory
- cert-portal.siemens.com/productcert/html/ssa-967325.htmlThird Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300US Government Resource
Sources
The verdict above is computed from the products and versions you entered and the affected ranges the vendor published to NVD. It does not inspect your environment, and this site never reports a product as unaffected: why.