SonicWall SonicOS Flaw Lets Attackers Bypass Access Controls and Crash Firewalls

SonicWall has released a security advisory detailing three new vulnerabilities affecting its SonicOS software.

Disclosed on April 29, 2026, under advisory ID SNWLID-2026-0004, these security flaws open the door for attackers to bypass access controls, manipulate restricted files, and intentionally crash critical firewall infrastructure.

The most severe of the three bugs carries a high-severity score, highlighting the need for immediate attention from network administrators.

While some exploits require the attacker already to have a foothold in the network or active credentials, the potential impact on network security and device availability is significant.

The Critical Access Control Flaw

The most dangerous vulnerability in this advisory is CVE-2026-0204. This improper access control flaw stems from weak authentication mechanisms within the SonicOS operating system.

Under specific conditions, an attacker operating on an adjacent network can bypass normal security checks to reach sensitive management interface functions.

While the attack requires some level of user interaction to trigger, the ability to access administrative functions without proper privileges poses a severe threat to network integrity.

If exploited, threat actors could modify firewall rules, alter security policies, or turn off vital protections entirely.

In addition to the access control issue, SonicWall patched two post-authentication vulnerabilities.

Because these flaws require an attacker to already have valid credentials on the firewall, their severity scores are slightly lower. Still, they remain dangerous tools for threat actors looking to escalate their access or disrupt operations.

The first is a path traversal vulnerability that lets an authenticated attacker interact with services that are usually restricted.

By manipulating file paths, the attacker can navigate outside of their intended directories to access unauthorized system areas. The second post-authentication flaw is a stack-based buffer overflow.

If a remote attacker sends too much data to a specific memory buffer, they can intentionally crash the SonicOS device, resulting in a denial-of-service condition that takes the firewall offline.

Vulnerability Breakdown

• CVE-2026-0204 has a CVSS score of 8.0, indicating an improper access control flaw that exposes management interface functions to unauthorized users on adjacent networks.
• CVE-2026-0205 has a CVSS score of 6.8 and is a post-authentication path-traversal bug that allows interaction with restricted underlying services.
• CVE-2026-0206 has a CVSS score of 4.9 and functions as a post-authentication stack-based buffer overflow that enables remote attackers to crash the firewall.

SonicWall confirms that workarounds are available for these vulnerabilities. Network administrators should immediately review the SNWLID-2026-0004 advisory to determine if their specific SonicOS versions are affected.

Organizations must apply the provided workarounds or official firmware patches as soon as possible to secure their management interfaces and protect their firewall uptime.

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