CVE-2026-0400 in SonicOS
Summary
by MITRE • 02/24/2026
A post-authentication Format String vulnerability in SonicOS allows a remote attacker to crash a firewall.
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Analysis
by VulDB Data Team • 02/28/2026
This vulnerability resides within SonicOS, a network security operating system developed by SonicWall, which serves as the foundation for their firewall and unified threat management appliances. The flaw manifests as a format string vulnerability that can be exploited by an attacker who has already gained authentication access to the system. This post-authentication requirement significantly reduces the attack surface compared to pre-authentication vulnerabilities, yet still represents a critical security risk within the network infrastructure. The vulnerability specifically affects the handling of user-supplied input within the application's logging or output functions, where improper formatting can lead to arbitrary code execution or system instability.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize user input before using it in format string operations. When authenticated users submit crafted input that contains format specifiers such as %s, %d, or %x, the system processes these without adequate validation or escaping mechanisms. This allows an attacker to manipulate the program's execution flow by reading from memory locations or writing to specific addresses, ultimately leading to a denial of service condition that crashes the firewall appliance. The vulnerability is particularly dangerous because it operates within the context of an authenticated session, meaning that an attacker who has already compromised credentials can leverage this weakness to disrupt network security services.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be exploited to create persistent denial of service conditions that compromise network availability and security posture. When the firewall crashes, network traffic is disrupted and security policies may be temporarily suspended, potentially allowing malicious activities to go undetected. The vulnerability also represents a potential stepping stone for more sophisticated attacks, as the attacker could use the crash condition to gain additional system information or attempt to exploit other weaknesses within the SonicOS environment. Organizations relying on SonicWall firewalls face significant risk of operational disruption, especially in environments where network uptime is critical for business continuity and security operations.
Mitigation strategies for this vulnerability should include immediate deployment of vendor-provided patches or firmware updates that address the format string handling issue. Network administrators should also implement additional monitoring and logging mechanisms to detect unusual authentication patterns or input behaviors that might indicate exploitation attempts. The principle of least privilege should be enforced by limiting administrative access and implementing multi-factor authentication to reduce the likelihood of unauthorized access. Organizations should also consider network segmentation and intrusion detection systems to monitor for potential exploitation attempts, as the vulnerability requires authentication to exploit, making it more difficult to detect through traditional perimeter security measures. This vulnerability aligns with CWE-134, which specifically addresses format string vulnerabilities in software applications, and could potentially map to ATT&CK technique T1499.004 for network disruption through service availability violations.