SonicWall has released an urgent security advisory (SNWLID-2026-0004) on April 29, 2026, disclosing three vulnerabilities affecting the Sonic operating system, which powers its entire Gen6, Gen7, and Gen8 firewall product lines.
The flaws, tracked as CVE-2026-0204, CVE-2026-0205, and CVE-2026-0206, collectively expose organizations to unauthorized access, path traversal attacks, and firewall denial-of-service conditions.
The vulnerabilities were discovered and responsibly disclosed by the Advanced Research Team at CrowdStrike.
Critical SonicWall SonicOS Vulnerability
The most critical flaw in this advisory, CVE-2026-0204, carries a CVSS v3 score of 8.0 (High) and is classified under CWE-1390 (Weak Authentication).
This vulnerability stems from a flaw in SonicOS’s access control mechanism that may allow certain management interface functions to remain accessible under specific conditions without proper authentication enforcement.
An adjacent-network attacker with no prior privileges could potentially exploit this flaw to gain high-impact access to confidentiality, integrity, and availability of the targeted system.
The second vulnerability, CVE-2026-0205 is a post-authentication path traversal vulnerability (CWE-35) with a CVSS score of 6.8.
An authenticated attacker can invoke a file download or API call using payloads such as ../../etc/passwd or URL-encoded %2e%2e%2f sequences.
This class of vulnerability is often leveraged as a stepping stone for deeper lateral movement within network infrastructure.
CVE-2026-0206 describes a post-authentication stack-based buffer overflow (CWE-121) with a CVSS score of 4.9.
A remote attacker with high-privilege credentials can send a specially crafted packet to a post-auth service such as the SSL-VPN component; the packet overflows a fixed-size stack buffer, causing an immediate firewall crash and full denial-of-service condition.
For organizations relying on SonicWall as their primary network perimeter control, this firewall outage could have severe cascading consequences on business continuity.
Affected Products and Versions
The vulnerabilities span all three current SonicWall firewall generations:
- Gen6 Hardware Firewalls (TZ 300/400/500/600 series, NSA series, SM series, SOHO series) versions 6.5.5.1-6n and older
- Gen7 Firewalls and NSv (TZ270–TZ670, NSa 2700–6700, NSsp series, NSv 270/470/870 on ESX, KVM, Hyper-V, AWS, Azure) versions 7.0.1-5169 and 7.3.1-7013 and older
- Gen8 Firewalls (TZ80–TZ680, NSa 2800–5800) versions 8.1.0-8017 and older
According to SonicWall’s (PSIRT), it strongly urges administrators to immediately turn off HTTP/HTTPS-based firewall management and SSL-VPN access on all interfaces, restricting management access exclusively to SSH.
Patched Firmware Versions
SonicWall has released fixed firmware across all affected generations:
- Gen6: 6.5.5.2-28n (Note: Downgrading from this version is unsupported and may reset all LDAP users and MFA configurations)
- Gen7: 7.3.2-7010
- Gen8: 8.2.0-8009
Security teams are strongly advised to apply these updates immediately, take a full configuration backup before upgrading Gen6 devices, and audit the exposure of the management interface across their SonicWall deployments.
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