CVE-2026-0300 Palo Alto Networks PAN-OS Out-of-bounds Write
Unauthenticated attackers can execute arbitrary code with root privileges on PAN-OS firewalls via a buffer overflow in the User-ID Authentication Portal.
- Exploited in the wild
- Since 6 May 2026
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-0300?
CVE-2026-0300 is a critical memory corruption vulnerability in Paloaltonetworks Pan-Os, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-0300?
It affects 2 products.
Products include Paloaltonetworks Pan-Os, Siemens Ruggedcom Ape1808 Firmware.
How do I fix CVE-2026-0300?
No fix has been published for CVE-2026-0300 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 9 May 2026.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-0300 being exploited?
Yes. Attackers have exploited CVE-2026-0300 in the wild since at least 6 May 2026.
Public exploit code: 10 proofs of concept on GitHub.
Other vulnerabilities in Paloaltonetworks Pan-Os
- CVE-2024-3400 Palo Alto Networks PAN-OS Command Injection
- CVE-2020-2021 Palo Alto Networks PAN-OS Authentication Bypass
- CVE-2017-15944 Palo Alto Networks PAN-OS Remote Code Execution
- CVE-2024-0012 Palo Alto Networks PAN-OS Management Interface Authentication Bypass
- CVE-2026-109618 PHP Memory Corruption
Sources
Also known as GHSA-3vfh-3cpw-2378.