In late July 2025, Arctic Wolf observed an increase in ransomware activity targeting SonicWall firewall devices for initial access. In the intrusions reviewed, multiple pre-ransomware intrusions were observed within a short period of time, each involving VPN access through SonicWall SSL VPNs.
While credential access through brute force, dictionary attacks, and credential stuffing have not yet been definitively ruled out in all cases, available evidence points to the existence of a zero-day vulnerability. In some instances, fully patched SonicWall devices were affected following credential rotation. Despite TOTP MFA being enabled, accounts were still compromised in some instances.
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Source: Arctic Wolf
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