Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
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.
- Vendor
- Palo Alto Networks
- Product
- PAN-OS
- CVSS
- 9.8
- EPSS (exploit probability)
- 41.7%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2026-0300 being exploited?
Yes. CISA added CVE-2026-0300 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 41.7% (scored October 25, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-11-13. Full cross-catalog view: /kev-comparison
CVE-2026-0300 timeline
- Added to CISA KEVsame day as NVD
- Published to NVD
Every event links to its source. Catalog dates are each catalog's own; day offsets count from NVD publication. Data: JSON
What to do
CISA required actionApply 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.
US federal civilian agencies must remediate by (3 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other Palo Alto Networks PAN-OS CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2026-0322 Palo Alto Networks PAN-OS Code Injection Vulnerabilitywrite-up | [ HIGH ] | — | 2.1% | |
| CVE-2026-0257 PAN-OS GlobalProtect authentication bypassransomware usewrite-up | [ CRITICAL ] | 9.1 | 95.6% | |
| CVE-2025-0111 Palo Alto Networks PAN-OS File Read Vulnerability | [ MEDIUM ] | 6.5 | 2.0% | |
| CVE-2025-0108 Palo Alto Networks PAN-OS Authentication Bypass Vulnerability | [ CRITICAL ] | 9.1 | 98.5% | |
| CVE-2024-3393 Palo Alto Networks PAN-OS Malicious DNS Packet Vulnerability | [ HIGH ] | 7.5 | 30.2% | |
| CVE-2024-9474 Palo Alto Networks PAN-OS Management Interface OS Command Injection Vulnerabilityransomware use | [ HIGH ] | 7.2 | 93.8% | |
| CVE-2024-0012 Palo Alto Networks PAN-OS Management Interface Authentication Bypass Vulnerabilityransomware use | [ CRITICAL ] | 9.8 | 99.8% | |
| CVE-2024-3400 Palo Alto Networks PAN-OS GlobalProtect Command Injection Zero-Dayransomware usewrite-up | [ CRITICAL ] | 10.0 | 100.0% |