CVE-2026-0321 in Cloud NGFW
Summary
by MITRE • 10/14/2026
Denial of service vulnerabilities in Palo Alto Networks PAN-OS® software allow an unauthenticated attacker with network access to cause a denial of service (DoS) condition by sending specially crafted network traffic to or through a dataplane interface. Repeated attempts to trigger this condition result in the firewall entering maintenance mode.
Cloud NGFW and Panorama are not affected by this vulnerability.
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Analysis
by VulDB Data Team • 10/14/2026
The identified security flaw represents a critical denial of service vulnerability within Palo Alto Networks PAN-OS software, specifically targeting the network dataplane interfaces. This weakness allows an unauthenticated attacker who possesses basic network connectivity to disrupt the availability of the firewall infrastructure. The mechanism involves sending specially crafted network traffic designed to exploit internal processing logic or resource allocation mechanisms within the device's data path. Unlike vulnerabilities that require authentication or complex exploitation chains, this flaw can be triggered by any external entity with reachability to the affected interface, significantly lowering the barrier for entry and increasing the likelihood of successful attacks in exposed environments.
The operational impact of this vulnerability is severe, characterized by a complete loss of service availability for the targeted firewall unit. When an attacker sends the malicious packets, they trigger conditions that overwhelm or corrupt internal processes responsible for handling network traffic. If these attempts are repeated, as often occurs during automated scanning or persistent attack campaigns, the system detects instability and initiates a fail-safe protocol known as maintenance mode. In this state, the firewall ceases to perform its primary function of inspecting and forwarding packets effectively, leading to a total disruption of network connectivity for all devices relying on that security appliance. This results in significant downtime and potential exposure of internal networks if no redundant high-availability pair is immediately available or properly configured to take over without interruption.
From a technical classification perspective, this vulnerability aligns with CWE-400, which describes uncontrolled resource consumption leading to denial of service conditions. The attack vector leverages the handling of specific packet structures that likely cause memory exhaustion, CPU spikes, or state table corruption within the dataplane processing engine. In terms of offensive security frameworks, this behavior corresponds to MITRE ATT&CK technique T1499, specifically endpoint disruption via resource exhaustion. The ability to trigger maintenance mode through crafted traffic indicates a failure in input validation and rate limiting mechanisms at the network interface level, allowing malicious payloads to bypass standard filtering rules before causing systemic instability.
It is important to note that this vulnerability does not affect Palo Alto Networks Cloud NGFW or Panorama management systems. This distinction highlights that the flaw is localized to specific on-premises hardware implementations running certain versions of PAN-OS where the dataplane processing logic resides directly within the appliance firmware rather than in cloud-based virtualized environments or centralized management consoles. Organizations utilizing these unaffected platforms are not at risk from this particular exploit vector, allowing for a more targeted remediation strategy focused solely on impacted physical appliances.
Mitigation strategies must prioritize immediate patching to the latest recommended version of PAN-OS provided by Palo Alto Networks, which includes fixes for the underlying code defects causing the resource exhaustion. In scenarios where immediate patching is not feasible due to operational constraints or testing requirements, network-level mitigations should be implemented. These include configuring access control lists on upstream routers or switches to restrict traffic from untrusted sources to the affected dataplane interfaces. Additionally, enabling rate limiting features available in PAN-OS can help mitigate the volume of crafted packets reaching the vulnerable processing logic. Regular monitoring for unusual spikes in CPU usage or memory consumption associated with specific network interfaces can also serve as an early detection mechanism for ongoing exploitation attempts, allowing security teams to respond before a full denial of service condition is reached.