CVEs / CVE-2026-0300
CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
- Known exploited in the CISA KEV catalog since 6 May 2026
- critical 9.8 CVSS 3.1 (NVD)
- EPSS 41.7% chance of exploitation in the next 30 days, higher than 98% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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 and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Palo Alto Networks PAN-OS | from 12.1.0, before 12.1.7 | 12.1.7 |
| Palo Alto Networks PAN-OS | from 11.2.0, before 11.2.12 | 11.2.12 |
| Palo Alto Networks PAN-OS | from 11.1.0, before 11.1.15 | 11.1.15 |
| Palo Alto Networks PAN-OS | from 10.2.0, before 10.2.18-h6 | 10.2.18-h6 |
| Siemens RUGGEDCOM APE1808 | all versions | — |
Exploitation
| In CISA KEV since | 6 May 2026 |
|---|---|
| Due date for US federal agencies | 9 May 2026 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|---|
| Weakness | CWE-787 |
References
- CVE-2026-0300 on NVD
- CVE-2026-0300 in the CISA KEV catalog
- https://security.paloaltonetworks.com/CVE-2026-0300 (cited by CISA)
- https://security.paloaltonetworks.com/CVE-2026-0300 Mitigation, Vendor Advisory
- 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
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.