CVE-2026-0402 is an out-of-bounds read vulnerability classified under CWE-125 found in SonicWall's SonicOS firmware. The vulnerability exists in multiple SonicOS versions, specifically 7.0.1-5169 and older, 7.3.1-7013 and older, and 8.1.0-8017 and older. It requires an attacker to have authenticated access with high privileges to trigger the flaw. The out-of-bounds read can cause the firewall device to crash, resulting in a denial-of-service (DoS) condition. The vulnerability does not allow for data disclosure or modification but impacts the availability of the firewall, potentially disrupting network security and connectivity. The CVSS v3.1 base score is 4.9, reflecting medium severity, with attack vector as network, low attack complexity, requiring privileges, no user interaction, and unchanged scope. No public exploits or active exploitation have been reported to date. The flaw likely stems from improper bounds checking in memory access routines within SonicOS, leading to reading memory outside intended buffers. This can destabilize the system and cause a crash. SonicWall has not yet published patches, so mitigation currently relies on access controls and monitoring.

The primary impact of CVE-2026-0402 is denial-of-service against SonicWall firewall devices, which can disrupt network traffic filtering and security enforcement. Organizations relying on affected SonicOS versions may experience temporary loss of firewall protection, potentially exposing internal networks to threats or causing business disruption. Critical infrastructure, enterprises, and service providers using SonicWall firewalls could face operational outages. Although confidentiality and integrity are not directly compromised, the availability impact can indirectly increase risk by disabling security controls. The requirement for authenticated access limits the threat to insiders or attackers who have already breached perimeter defenses. However, once exploited, the attacker can cause repeated firewall crashes, complicating incident response and recovery. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as patches are not yet available.

Organizations should immediately audit and restrict administrative access to SonicWall devices, ensuring only trusted personnel can authenticate. Implement network segmentation and VPNs to limit access to management interfaces. Monitor firewall logs and system stability for signs of exploitation attempts or crashes. Maintain up-to-date backups of firewall configurations to enable rapid recovery. Engage with SonicWall support to track patch release schedules and apply firmware updates promptly once available. Consider deploying additional perimeter defenses to reduce the risk of attackers gaining authenticated access. Employ multi-factor authentication for firewall management accounts to reduce the likelihood of credential compromise. Conduct regular vulnerability assessments and penetration testing to identify potential exposure. Document incident response plans specifically for firewall outages to minimize downtime.