CVE-2026-0300: in the CISA KEV catalogue

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability. CISA added CVE-2026-0300 to the Known Exploited Vulnerabilities catalogue on 2026-05-06 with a default due date of 2026-05-09. Known ransomware campaign use: Unknown. Forensic triage flag: No.

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. (CISA description)

Vendor / product: Palo Alto Networks PAN-OS
CWE: CWE-787
CISA 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.
EPSS: 42%, percentile 98 (scored 2026-11-03)

EPSS puts about 42 in 100 odds (42%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 98% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.03, released 2026-11-03, 1,767 entries (checked 2026-11-03). EPSS model v2026.06.15, scored 2026-11-03, 399,388 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2026-0300 in the CISA KEV catalogue?

Yes. CISA added CVE-2026-0300 (Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-05-06. CISA's default due date for it is 2026-05-09.

Is CVE-2026-0300 used in ransomware attacks?

CISA marks known ransomware campaign use as Unknown for CVE-2026-0300. That means CISA lacks confirmation, not that ransomware groups do not use it.

What should I do about CVE-2026-0300?

CISA's 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.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2026-0300