CVE-2026-0300
CriticalExploitedPublic exploitA 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…
Published May 7, 2026 · Updated Oct 15, 2026 · Also known as TR-26-0179
Key Facts
Patch immediately- CVE-2026-0300 is a critical-severity vulnerability (CVSS 9.3 v4) affecting PAN-OS (Palo Alto Networks), Ruggedcom Ape1808 Firmware (Siemens), Cloud NGFW and 1 more product.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 5, 2026 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 32% probability of exploitation in the next 30 days.
- Fixed versions are available, including PAN-OS 10.2.10-h36, PAN-OS 10.2.13-h21, PAN-OS 10.2.16-h7.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v4
9.3
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:C/RE:M/U:Red
EPSS (30-day exploit likelihood)
32%
Higher than 98.2% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | May 6, 2026 | May 9, 2026 | Not reported |
| Industry KEV feed | May 5, 2026 | May 9, 2026 | Known |
| CIRCL KEV | May 6, 2026 | May 9, 2026 | Not reported |
| ENISA EUVD | May 6, 2026 | n/a | Not reported |
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.
Affected Products
227 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| PAN-OSPalo Alto Networks | 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 | 12.1.4-h5 |
| Ruggedcom Ape1808 FirmwareSiemens | See advisory | n/a |
| Cloud NGFW | See advisory | n/a |
| Prisma Access | See advisory | n/a |
Patched Releases
PAN-OS
10.2.10-h36, 10.2.13-h21, 10.2.16-h7, 10.2.18-h6, 10.2.7-h34, 11.1.10-h25, 11.1.13-h5, 11.1.15, 11.1.4-h33, 11.1.6-h32, 11.1.7-h6, 11.2.10-h6, 11.2.12, 11.2.4-h17, 11.2.7-h13, 12.1.4-h5, 12.1.7
Timeline
Added to Industry KEV feed
May 5, 2026
Added to CISA KEV
May 6, 2026
Added to CIRCL KEV
May 6, 2026
Added to ENISA EUVD
May 6, 2026
Publicly disclosed
May 7, 2026
Last updated
Oct 15, 2026
Weakness Type
- CWE-787 Out-of-bounds Write
References
- advisoryhttps://cert-portal.siemens.com/productcert/html/ssa-967325.html
- advisoryhttps://security.paloaltonetworks.com/
- advisoryVulnCheck exploitation report
- advisoryhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-0300
- advisoryUSOM advisory
FAQ
Common Questions.
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.
Affected: PAN-OS (Palo Alto Networks) versions 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; Ruggedcom Ape1808 Firmware (Siemens); Cloud NGFW, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 5, 2026 and is known to be used in ransomware campaigns.
Yes. It was added on May 6, 2026 with a federal remediation due date of May 9, 2026.
Public exploit code is available.
Fixed versions are available, including PAN-OS 10.2.10-h36, PAN-OS 10.2.13-h21, PAN-OS 10.2.16-h7.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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