- SonicWall Patches SSLVPN CVE-2025-40601 Flaw, Allowing Unauthenticated DoS Attacks on Gen7/Gen8 Firewalls
- Exploitation has not yet been seen; Users are urged to disable SSLVPN or restrict access if updates are delayed.
- Also fixed two flaws in the Email Security device (CVE-2025-40604/40605), which prevented code execution and data access.
SonicWall released a patch for a high severity vulnerability in its SonicOS SSLVPN service and urged all users to update their firewalls immediately.
In a security advisory, the company said it discovered a stack-based buffer overflow vulnerability in SonicOS’s SSLVPN service, which allows an unauthenticated, remote attacker to cause Denial of Service (DoS) and essentially crash the firewall.
The vulnerability is now tracked as CVE-2025-40601 and has been assigned a severity score of 7.5/10 (High). It affects Gen8 and Gen7 firewalls, both hardware and virtual. Previous models, such as Gen6 firewalls or SMA 1000 and SMA 100 series SSL VPN products, were said to be safe from this bug.
SonicWall also noted that the bug only affects the SSLVPN interface or service, if it is enabled on the firewall.
No evidence or PoC
There is no evidence that this vulnerability is being exploited naturally, but cybercriminals often wait for a bug to become public before attacking.
Finding zero-day flaws is difficult and many companies do not patch their technologies in time, leaving the door open to attackers. Until now, there has been no proof of concept (PoC) on the Internet.
If you are unable to update your firewall at this time, you should disable the SonicOS SSLVPN service or update the rules to limit access to SonicWall firewall applications to only trusted sources, as firewalls are one of the most popular targets for cybercriminals.
At the same time, SonicWall also fixed two vulnerabilities in its email security appliances (ES Appliance 5000, 5050, 7000, 7050, 9000, VMWare and Hyper-V), tracked as CVE-2025-40604 and CVE-2025-40605. These allow threat actors to gain persistent arbitrary code execution capabilities as well as access to restricted information.
For this patch, SonicWall also “strongly recommended” users to install it without hesitation.
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