Palo Alto Networks has released security patches to address a high severity denial of service vulnerability affecting its PAN OS next generation firewall software, warning that the issue could allow unauthenticated attackers to disrupt critical network infrastructure. The flaw, tracked as CVE-2026-0227, impacts GlobalProtect gateway and portal configurations that are widely deployed to support remote access in enterprise environments. According to the vendor, successful exploitation can force affected firewalls into maintenance mode, resulting in service disruption and loss of availability for users who rely on secure connectivity.
The vulnerability was publicly disclosed on January 14, 2026, and carries a CVSS v4.0 base score of 7.7, placing it in the high severity category. When environmental metrics are applied, the score increases to 8.7, reflecting the potential impact on organizations with exposed deployments. Palo Alto Networks explained that the issue originates from improper validation of unusual or exceptional conditions within PAN OS, which allows repeated exploitation attempts to overwhelm system processes. Security researchers have confirmed that the flaw can be exploited remotely over the network with low attack complexity, without requiring authentication credentials or any user interaction. This combination significantly raises the risk profile, as automated tools could be used to target large numbers of exposed systems simultaneously. The vulnerability maps to CWE 754, improper check for unusual or exceptional conditions, and aligns with CAPEC 210, abuse of existing functionality.
While the vulnerability does not affect data confidentiality or integrity, its impact on availability is considered severe, as it can take firewalls offline and interrupt business operations. Palo Alto Networks has acknowledged that proof of concept exploit code exists within the security research community, although its Product Security Incident Response Team has stated that there is no confirmed evidence of active malicious exploitation at the time of the advisory. Analysts have, however, observed scanning activity that may suggest adversaries are probing for vulnerable systems. The issue affects PAN OS firewall deployments and Prisma Access environments where a GlobalProtect gateway or portal is enabled. Cloud NGFW customers are not affected and do not need to take action.
Multiple PAN OS branches are impacted across both current and legacy releases. Affected versions include PAN OS 12.1 releases earlier than 12.1.3 h3 and 12.1.4, PAN OS 11.2 versions prior to 11.2.4 h15, 11.2.7 h8, and 11.2.10 h2, as well as PAN OS 11.1 releases earlier than 11.1.4 h27, 11.1.6 h23, 11.1.10 h9, and 11.1.13. Older PAN OS 10.2 versions before 10.2.7 h32, 10.2.10 h30, 10.2.13 h18, 10.2.16 h6, and 10.2.18 h1 are also affected. Prisma Access deployments running versions below 11.2.7 h8 are similarly vulnerable. Palo Alto Networks has released corresponding patched versions for each affected branch and confirmed that no workaround or configuration change can mitigate the issue without applying updates.
Although the vendor has classified the remediation urgency as moderate, it has urged organizations to prioritize upgrades due to the lack of alternative protections. PAN OS 12.1 customers are advised to upgrade to version 12.1.4 or later, while PAN OS 11.2 users should deploy hotfix 11.2.10 h2 or newer. Prisma Access customers generally benefit from automated upgrade scheduling, with many environments already updated. Security teams are advised to verify their GlobalProtect configurations through the Palo Alto Networks support portal and monitor for unexpected maintenance mode events or abnormal firewall behavior, particularly in environments where immediate patching may be delayed.
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