CVE-2026-0402: SonicWall SonicOS DoS Vulnerability

CVE-2026-0402 Overview

CVE-2026-0402 is a post-authentication Out-of-bounds Read vulnerability affecting SonicWall SonicOS firmware across multiple firewall product lines. This memory corruption flaw allows a remote attacker with valid authentication credentials to crash the firewall appliance, resulting in a denial of service condition that can disrupt network security operations.

The vulnerability exists in the SonicOS firmware and requires the attacker to first authenticate to the firewall management interface before exploitation. While the authentication requirement limits the attack surface, organizations with compromised administrative credentials or insider threat scenarios remain at risk of service disruption.

Critical Impact

Authenticated attackers can remotely crash SonicWall firewalls, causing network security disruption and potential loss of protection for connected systems.

Affected Products

• SonicWall SonicOS (multiple versions)
• SonicWall NSA Series (NSA 2700, NSA 3700, NSA 4700, NSA 5700, NSA 6700, NSA 2800, NSA 3800, NSA 4800, NSA 5800)
• SonicWall NSSP Series (NSSP 10700, NSSP 11700, NSSP 13700, NSSP 15700)
• SonicWall NSv Series (NSv270, NSv470, NSv870)
• SonicWall TZ Series (TZ80, TZ270, TZ270W, TZ280, TZ370, TZ370W, TZ380, TZ470, TZ470W, TZ480, TZ570, TZ570P, TZ570W, TZ580, TZ670, TZ680)

Discovery Timeline

• February 24, 2026 - CVE-2026-0402 published to NVD
• February 26, 2026 - Last updated in NVD database

Technical Details for CVE-2026-0402

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), a memory safety issue where the software reads data past the end of an intended buffer. In the context of SonicOS, this occurs when processing certain requests after a user has authenticated to the firewall's management interface.

Out-of-bounds read vulnerabilities can have varying impacts depending on the affected code path. In this case, the out-of-bounds memory access causes the SonicOS firmware to crash, resulting in a denial of service condition. When the firewall crashes, all network traffic routing and security inspection functions are interrupted until the device recovers or is manually restarted.

The post-authentication requirement means attackers must first obtain valid credentials to the SonicWall management interface before triggering the vulnerability. This could occur through credential theft, phishing attacks targeting administrators, or insider threat scenarios.

Root Cause

The root cause of CVE-2026-0402 is improper bounds checking in SonicOS when handling certain authenticated requests. The firmware fails to validate that memory read operations remain within allocated buffer boundaries, allowing reads beyond the intended data structure. When invalid memory regions are accessed, this triggers an unhandled exception that crashes the firewall service.

Attack Vector

The attack vector for this vulnerability is network-based, requiring the attacker to:

1. Obtain valid authentication credentials for the SonicWall management interface
2. Establish an authenticated session with the target firewall
3. Send specially crafted requests that trigger the out-of-bounds read condition
4. The vulnerable code path reads past buffer boundaries, causing a crash

Since this is a denial of service vulnerability affecting a firewall's availability, the primary concern is disruption of network security services. Successful exploitation does not result in data exfiltration or code execution, but the crash condition removes the firewall from the network path, potentially exposing protected systems.

For technical details on the vulnerability, refer to the SonicWall Security Advisory SNWLID-2026-0001.

Detection Methods for CVE-2026-0402

Indicators of Compromise

• Unexpected firewall reboots or service restarts without scheduled maintenance
• Authentication events from unusual source IP addresses followed by device crashes
• Repeated crash events in SonicOS system logs correlating with administrative sessions
• Unusual patterns of management interface access attempts

Detection Strategies

• Monitor SonicOS system logs for crash events and correlate with recent authentication activity
• Implement alerting for firewall unavailability or unscheduled restarts
• Review management interface access logs for authentication from unexpected sources
• Deploy network monitoring to detect gaps in firewall availability

Monitoring Recommendations

• Enable comprehensive logging on all SonicWall management interface authentication events
• Configure SNMP traps or syslog forwarding to detect firewall unavailability
• Implement heartbeat monitoring for critical firewall appliances
• Review administrative access patterns and credentials regularly

How to Mitigate CVE-2026-0402

Immediate Actions Required

• Review SonicWall's security advisory and apply available patches to affected firmware versions
• Audit administrative credentials and revoke any potentially compromised accounts
• Restrict management interface access to trusted IP addresses only
• Enable multi-factor authentication for all administrative accounts

Patch Information

SonicWall has released security updates addressing this vulnerability. Organizations should consult the SonicWall Security Advisory SNWLID-2026-0001 for specific patched firmware versions applicable to their hardware models. Upgrade SonicOS to the latest available version that addresses CVE-2026-0402.

Workarounds

• Restrict management interface access to a dedicated management VLAN or jump host
• Implement IP-based access control lists limiting management access to authorized administrator workstations
• Enable strong authentication mechanisms and enforce complex password policies
• Consider disabling remote management access when not actively required

# Example: Restrict management access to specific IP addresses (conceptual)
# Configure access rules on SonicWall to limit management interface access
# Consult SonicWall documentation for specific CLI commands
# 
# General approach:
# 1. Define trusted management IP addresses
# 2. Create access rules blocking management ports from untrusted sources
# 3. Enable logging for all management access attempts