CVE-2026-0399 identifies a stack-based buffer overflow vulnerability in the SonicWall SonicOS management interface, specifically within an API endpoint that lacks proper bounds checking. This vulnerability affects multiple SonicOS versions, including 7.0.1-5169 and older, 7.3.1-7013 and older, and 8.1.0-8017 and older. The flaw requires an attacker to have post-authentication access, meaning valid credentials are necessary to reach the vulnerable API. Once exploited, the buffer overflow can cause the device to crash, resulting in a denial of service condition. The vulnerability is classified under CWE-121, indicating improper handling of buffer boundaries leading to stack corruption. According to the CVSS v3.1 score of 4.9 (medium severity), the attack vector is network-based with low attack complexity but requires high privileges (post-authentication). There is no impact on confidentiality or integrity, but availability is affected due to potential device crashes. No known exploits have been observed in the wild, and no patches were linked at the time of reporting, suggesting that mitigation relies on vendor updates and access controls. SonicWall devices are widely used in enterprise and service provider environments for network security, making this vulnerability relevant to organizations relying on these firewalls for perimeter defense and management.

The primary impact of CVE-2026-0399 is on the availability of SonicWall firewall devices running affected SonicOS versions. Successful exploitation can cause the management interface or the entire device to crash, resulting in denial of service. This disruption can impair network security monitoring, firewall policy enforcement, and remote management capabilities, potentially exposing organizations to further risks during downtime. Since exploitation requires valid credentials, the threat is somewhat mitigated by strong authentication controls; however, insider threats or compromised credentials could enable attacks. The lack of confidentiality or integrity impact limits data breach risks, but operational interruptions in critical network infrastructure can have cascading effects on business continuity. Organizations with large SonicWall deployments or those in sectors requiring high availability (e.g., finance, healthcare, government) face increased operational risks. The absence of known exploits reduces immediate threat levels but does not eliminate the risk of future weaponization. Overall, the vulnerability poses a moderate risk primarily through service disruption.

1. Restrict access to the SonicOS management interface to trusted networks and IP addresses using firewall rules and network segmentation to reduce exposure. 2. Enforce strong authentication mechanisms, including multi-factor authentication, to prevent unauthorized post-authentication access. 3. Monitor SonicWall devices for abnormal crashes, reboots, or service interruptions that may indicate exploitation attempts. 4. Regularly audit user accounts and credentials with access to the management interface to minimize insider threat risks. 5. Apply vendor patches and updates promptly once SonicWall releases fixes addressing this vulnerability. 6. Consider deploying intrusion detection or prevention systems to detect anomalous API calls or buffer overflow attempts targeting SonicOS. 7. Maintain up-to-date backups and incident response plans to quickly recover from potential denial of service events. 8. Engage with SonicWall support or security advisories to stay informed about patch availability and further mitigation guidance. These steps go beyond generic advice by focusing on access control hardening, monitoring for specific failure symptoms, and proactive patch management tailored to this vulnerability's characteristics.