CVE-2021-20035 is a security vulnerability identified in the SonicWall SMA100 series, specifically affecting versions 9.0.0.10-28sv and earlier, 10.2.0.7-34sv and earlier, and 10.2.1.0-17sv and earlier. The vulnerability is classified as CWE-78, which corresponds to improper neutralization of special elements used in an OS command, commonly known as OS command injection. This flaw exists in the SMA100 management interface, where insufficient sanitization of user input allows a remote attacker with authenticated access to inject arbitrary operating system commands. The commands are executed with the privileges of the 'nobody' user, a low-privilege account typically used to limit potential damage. Despite the limited privileges, successful exploitation can lead to denial of service (DoS) conditions, potentially disrupting the availability of the SMA100 device and its managed services. The vulnerability does not require user interaction beyond authentication, and the attack vector is network-based, making it accessible remotely. The CVSS v3.1 base score is 6.5, indicating a medium severity level, with the vector string AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, meaning the attack can be performed remotely with low attack complexity, requires privileges, no user interaction, unchanged scope, no confidentiality or integrity impact, but high impact on availability. No known exploits have been reported in the wild as of the published date. The lack of patch links suggests that remediation may require vendor intervention or updates that should be sought from SonicWall directly.

For European organizations, the impact of CVE-2021-20035 can be significant, especially for those relying on SonicWall SMA100 appliances for secure remote access and network management. The SMA100 is often deployed as a secure mobile access gateway, and disruption due to a DoS attack could result in loss of remote connectivity, hindering business continuity and operational efficiency. While the vulnerability does not allow data theft or modification, the availability impact can affect critical services, particularly for sectors requiring continuous remote access such as finance, healthcare, and government. Additionally, the requirement for authenticated access means that attackers would need valid credentials, but insider threats or compromised accounts could be leveraged to exploit this vulnerability. The medium severity rating suggests that while the threat is not immediately critical, it should not be ignored, especially in environments where uptime and secure remote access are paramount. European organizations with compliance obligations under regulations like GDPR must consider the operational risks and potential indirect compliance impacts due to service disruptions.

To mitigate CVE-2021-20035, European organizations should first verify the firmware version of their SonicWall SMA100 devices and upgrade to the latest available version provided by SonicWall that addresses this vulnerability. If an official patch is not yet available, organizations should implement strict access controls to limit management interface access only to trusted administrators and networks, ideally via VPN or other secure channels. Multi-factor authentication (MFA) should be enforced to reduce the risk of credential compromise. Monitoring and logging of management interface access should be enhanced to detect any anomalous or unauthorized activities promptly. Network segmentation can be employed to isolate the SMA100 management interface from general user networks, reducing exposure. Additionally, organizations should conduct regular vulnerability assessments and penetration testing focused on the SMA100 appliances to identify potential exploitation attempts. Finally, incident response plans should be updated to include scenarios involving DoS attacks on remote access infrastructure to ensure rapid recovery.