CVE-2026-0279 in Captive Portal
Summary
by MITRE • 07/09/2026
Multiple cross site scripting vulnerabilities in the User-ID™ Authentication Portal (aka Captive Portal) service, GlobalProtect™ gateway/portal features and Clientless VPN of Palo Alto Networks PAN-OS® software enables a malicious unauthenticated user to store or execute malicious JavaScript payload.
The security risk posed by this issue is minimized when the management interface and access to the User-ID™ Authentication Portal is restricted to only trusted internal IP addresses according to our recommended best practice deployment guidelines https://live.paloaltonetworks.com/t5/community-blogs/tips-amp-tricks-how-to-secure-the-management-access-of-your-palo/ba-p/464431 .
This issue is applicable to PAN-OS software on PA-Series and VM-Series firewalls and on Panorama (virtual and M-Series).
Cloud NGFW is not affected by this vulnerability.
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Analysis
by VulDB Data Team • 07/09/2026
This cross site scripting vulnerability affects Palo Alto Networks PAN-OS software across multiple components including the User-ID Authentication Portal, GlobalProtect gateway/portal features, and Clientless VPN functionality. The flaw allows unauthenticated malicious actors to inject and execute arbitrary JavaScript payloads through the affected services, representing a significant security risk that could compromise user sessions and system integrity. According to CWE-79, this vulnerability maps directly to Cross-Site Scripting (XSS) flaws where improperly sanitized input is reflected back to users in web pages. The ATT&CK framework categorizes this under T1059.007 for Command and Scripting Interpreter with JavaScript payloads.
The technical implementation of these vulnerabilities stems from insufficient input validation and output encoding mechanisms within the web interfaces of PAN-OS components. Attackers can exploit these flaws by crafting malicious payloads that get stored or executed when legitimate users interact with affected portals. This creates a persistent threat vector where even unauthenticated users can manipulate the web application behavior to execute arbitrary code in the context of other users' browsers. The impact extends beyond simple script execution as it can enable session hijacking, credential theft, and potential lateral movement within the network environment.
The operational implications are severe for organizations relying on Palo Alto firewalls, particularly those with exposed management interfaces or unrestricted access to authentication portals. When users authenticate through affected services, their sessions become vulnerable to manipulation, potentially allowing attackers to gain unauthorized access to protected resources. The vulnerability affects both PA-Series hardware firewalls and VM-Series virtual appliances, as well as Panorama management platforms across different deployment models including M-Series hardware and virtual instances.
Organizations should implement immediate mitigations including restricting management interface access to trusted internal IP addresses as recommended by Palo Alto Networks best practices. Network segmentation and access controls must be enforced to limit exposure of User-ID Authentication Portal services to untrusted networks. Additional protective measures include implementing web application firewalls, monitoring for suspicious JavaScript payloads, and ensuring regular security updates are applied. The vulnerability highlights the importance of principle of least privilege in network security configurations, where administrative interfaces should never be exposed to public internet access without proper authentication and authorization controls.
The affected PAN-OS software versions require careful assessment and remediation planning since Cloud NGFW deployments remain unaffected by this specific vulnerability. Security teams must conduct comprehensive vulnerability assessments across all Palo Alto Networks installations to identify systems potentially vulnerable to these XSS attacks. Regular security monitoring should be implemented to detect anomalous JavaScript activity in portal services, while incident response procedures should be updated to address potential exploitation attempts. This vulnerability serves as a reminder of the critical importance of web application security controls in enterprise network infrastructure components where user authentication and access management reside.