SonicWall Warns of New SonicOS SSLVPN Pre-Auth Buffer Overflow Vulnerability (CVE-2025-40601)

SonicWall has issued a security advisory for a newly identified pre-authentication stack-based buffer overflow in its SonicOS SSLVPN service, tracked as CVE-2025-40601 with a CVSS score of 7.5. The flaw could allow remote, unauthenticated attackers to crash affected firewalls, potentially disrupting business-critical network access.

According to the advisory, a stack-based buffer overflow in the SonicOS SSLVPN service allows a remote unauthenticated attacker to cause Denial of Service, which could cause an impacted firewall to crash. The vulnerability affects multiple generations of SonicWall hardware and virtual firewalls, with fixed versions released for all affected platforms.

Affected Gen7 hardware Firewalls include TZ270, TZ270W, TZ370, TZ370W, TZ470, TZ470W, TZ570, TZ570W, TZ570P, TZ670, NSa 2700, NSa 3700, NSa 4700, NSa 5700, NSa 6700, NSsp 10700, NSsp 11700, NSsp 13700, NSsp 15700, and Gen7 virtual Firewalls (NSv) – NSV270, NSv470, NSv870 (ESX, KVM, HYPER-V, AWS, Azure); Gen8 Firewalls include TZ80, TZ280, TZ380, TZ480, TZ580, TZ680, NSa 2800, NSa 3800, NSa 4800, NSa 5800, with 8.0.2-8011 and older versions affected.

Until patches can be deployed, SonicWall recommends a straightforward temporary mitigation: limit SonicOS SSLVPN access to trusted sources (and/or disable firewall SSLVPN service from untrusted internet sources) by modifying existing SSLVPN access rules.