SonicWall VPN zero-day attacks put businesses at ransomware risk

SonicWall VPN zero-day vulnerabilities are putting businesses on high alert as cybercriminals exploit the flaw to deploy ransomware. Cybersecurity researchers have observed a surge in malicious VPN logins since mid-July 2025, raising concerns that attackers may have discovered a previously unknown vulnerability in SonicWall SSL VPN devices. For businesses relying on these VPNs, understanding the threat and implementing immediate protective measures is crucial to avoid falling victim to ransomware like Akira.

Rising ransomware attacks targeting SonicWall VPN

Researchers from Arctic Wolf Labs reported a noticeable increase in unauthorized logins targeting SonicWall VPN instances, with some devices compromised despite being fully patched. This pattern strongly suggests a potential SonicWall VPN zero-day exploit. Shortly after these suspicious logins, victims reported Akira ransomware infections, confirming the attackers’ intent to rapidly encrypt systems after gaining access. Cybercriminals are likely leveraging either stolen credentials or an undisclosed vulnerability to bypass security.

How cybercriminals are exploiting SonicWall VPNs

Attackers are using methods that differ from legitimate VPN logins, often connecting through Virtual Private Server (VPS) hosts rather than home internet providers. This tactic allows them to mask their locations and avoid detection. Once they gain initial access, the attackers move swiftly to deploy Akira ransomware. The malware, first seen in 2023, specifically targets businesses by exploiting exposed VPNs and weak remote access points. Its rapid encryption process leaves companies little time to respond, emphasizing the importance of proactive security.

How businesses can protect against SonicWall VPN attacks

Until SonicWall releases a patch or confirms the nature of the zero-day vulnerability, organizations must strengthen their defenses. Experts recommend enabling multi-factor authentication (MFA), regularly updating passwords with strong and unique credentials, and removing unused or inactive firewall accounts. These measures reduce the attack surface and make it harder for threat actors to compromise networks. Vigilance and proactive monitoring are essential, as SonicWall VPN zero-day exploits can quickly escalate to costly ransomware incidents