Analysis Summary

A set of critical vulnerabilities has been identified in SonicWall SMA 100 series SSL-VPN appliances, potentially allowing remote, unauthenticated attackers to execute arbitrary JavaScript or system-level code. These flaws impact SMA 210, 410, and 500v models running firmware versions up to 10.2.1.15-81sv, exposing affected organizations to significant security threats. The vulnerabilities include two high-severity buffer overflow issues and one medium-severity XSS flaw, all exploitable over the network without prior authentication. If left unpatched, these weaknesses can be leveraged for denial-of-service attacks or even full remote code execution.

The first two vulnerabilities, CVE-2025-40596 and CVE-2025-40597, are pre-authentication buffer overflows, stack-based and heap-based, respectively, both scoring (High) on the CVSS scale. These flaws, classified under CWE-121 and CWE-122, can be triggered by sending specially crafted requests to the SMA web interface, requiring no prior access or user interaction. Their shared CVSS vector (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L) indicates the simplicity of exploitation, making these vulnerabilities particularly dangerous in unprotected environments.

The third vulnerability, CVE-2025-40598, is a reflected cross-site scripting (XSS) flaw categorized under CWE-79, with a CVSS score of (Medium). While this issue does require some level of user interaction, typically involving the victim clicking on a crafted malicious link, it still poses a serious risk as it enables attackers to inject and execute arbitrary JavaScript within the victim's browser, leading to potential session hijacking or phishing attacks.

To mitigate these threats, SonicWall urges all users of the affected SMA 100 series devices to upgrade immediately to firmware version 10.2.2.1-90sv or newer. While no active exploitation has been reported as of now, the pre-authentication nature of the vulnerabilities necessitates urgent patching. As additional protective measures, organizations are advised to enable multi-factor authentication (MFA) and activate the built-in Web Application Firewall (WAF) feature to reduce exposure to credential-based attacks and HTTP-level exploits. Notably, these issues do not affect the SonicWall SMA 1000 series or SSL-VPN functionality embedded within SonicWall firewalls. The vulnerabilities were responsibly disclosed by researcher.

Impact

• Buffer Overflow
• Cross-site Scripting
• Code Execution

Indicators of Compromise

CVE

• CVE-2025-40596

• CVE-2025-40597

• CVE-2025-40598

Affected Vendors

Remediation

• Refer to SonicWall Security Advisory for patch, upgrade or suggested workaround information.
• Enable Multi-Factor Authentication (MFA) on the SMA appliance or through integrated directory services to prevent unauthorized access.
• Activate the Web Application Firewall (WAF) feature on SMA 100 devices to provide additional protection against web-based exploits.
• Monitor for signs of exploitation even though no active attacks have been reported, due to the pre-authentication nature of the vulnerabilities.
• Restrict access to the management interface using network-level controls or VPN whitelisting.
• Regularly audit appliance logs for suspicious traffic or abnormal login attempts.
• Stay updated with SonicWall’s security advisories and threat intelligence reports for any new developments.