Analysis Summary

A newly discovered medium-severity vulnerability, CVE-2025-40600, affects SonicWall Gen7 firewall products by allowing remote, unauthenticated attackers to launch denial-of-service (DoS) attacks through the SSL VPN interface. This format string vulnerability (CWE-134), tracked internally as SNWLID-2025-0013, is caused by improper handling of externally-controlled format strings in printf-style functions. If successfully exploited, it can lead to memory corruption and application crashes, impacting system availability without compromising data confidentiality or integrity. The vulnerability is network-accessible, does not require user interaction or authentication, and has been assigned a CVSS score of medium, indicating moderate severity with high impact on availability.

The flaw specifically affects SonicOS version 7.2.0-7015 and older, leaving both hardware and virtual Gen7 firewall models exposed. Impacted hardware includes the TZ, NSa, and NSsp series, while virtual environments such as NSv270, NSv470, and NSv870 on ESX, KVM, HYPER-V, AWS, and Azure are also vulnerable. Systems running the SonicOS 7.0.1 branch or newer than 7.3.0-7012 are not affected, and other SonicWall product lines such as Gen6, Gen8, and the SMA 100/1000 series remain unaffected.

To mitigate the risk, SonicWall has issued patched software (version 7.3.0-7012 and above). Organizations that cannot immediately upgrade are advised to disable the SSL VPN interface as a temporary workaround. It’s important to note that firewalls with SSL VPN functionality turned off are not at risk, and the attack complexity remains high due to the required remote access and format string manipulation.

Given the nature of this vulnerability, organizations that rely on SonicWall Gen7 firewalls for secure remote access should act promptly. While the vulnerability does not enable data theft or privilege escalation, it poses a serious availability threat to affected network infrastructure. Security teams are urged to identify exposed VPN interfaces, update to the latest firmware where possible, and disable SSL VPN access temporarily to prevent potential service disruptions.

Impact

• Denial of Service

Indicators of Compromise

CVE

• CVE-2025-40600

Affected Vendors

Remediation

• Upgrade to SonicOS version 7.3.0-7012 or later to patch the vulnerability.
• Disable the SSL VPN interface as a temporary workaround if immediate upgrading is not possible.
• Restrict remote access to the SSL VPN interface using firewall rules or access control lists (ACLs).
• Monitor logs for unusual activity or repeated service crashes on the SSL VPN interface.
• Identify and audit all Gen7 firewalls and virtual appliances running SonicOS 7.2.0-7015 or older.
• Segment critical infrastructure from internet-facing interfaces to reduce potential attack impact.
• Disable any unused or unnecessary services on SonicWall firewalls to minimize the attack surface.
• Notify internal IT and security teams about the vulnerability and current mitigation actions.
• Regularly check SonicWall’s official advisory page for updates and additional patches.
• Review and document all firewall configurations and mitigation steps to ensure consistent protection.