Palo Alto Cloud NGFW/PAN-OS/Prisma Access out-of-bounds write

Summaryinfo

A vulnerability has been found in Palo Alto Cloud NGFW, PAN-OS and Prisma Access and classified as critical. Impacted is an unknown function. Performing a manipulation results in out-of-bounds write. This vulnerability is reported as CVE-2026-0300. The attack is possible to be carried out remotely. Moreover, an exploit is present.

Detailsinfo

A vulnerability was found in Palo Alto Cloud NGFW, PAN-OS and Prisma Access (the affected version unknown). It has been classified as very critical. This affects an unknown part. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. CWE is classifying the issue as CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at security.paloaltonetworks.com. This vulnerability is uniquely identified as CVE-2026-0300 since 11/03/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are unknown but an exploit is available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/13/2026).

It is declared as attacked. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 05/06/2026 with a due date of 05/09/2026:

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

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Zero-Day.cz (1094) and EUVD (EUVD-2026-27879). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Firewall Software

Vendor

• Palo Alto

Name

• Cloud NGFW
• PAN-OS
• Prisma Access

License

• commercial

Website

• Vendor: https://www.paloaltonetworks.com/

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