These appliances, although no longer supported with updates, remain in operation at many organizations, making them attractive to cybercriminals. The hacking group behind these intrusions has been named UNC6148 by Google.
Despite being end-of-life, the devices still sit on the edge of sensitive networks, and their continued use has led to increased risk exposure.
GTIG is urging all organizations that rely on these SMA appliances to examine them for signs of compromise. They recommend that firms collect complete disk images for forensic analysis, as the attackers are believed to be using rootkit-level tools to hide their tracks, potentially tampering with system logs. Assistance from SonicWall may be necessary for acquiring these disk images from physical devices.
There is currently limited clarity around the technical specifics of these breaches.
The attackers are leveraging leaked administrator credentials to gain access, though it remains unknown how those credentials were originally obtained. It’s also unclear what software vulnerabilities are being exploited to establish deeper control. One major obstacle to understanding the attacks is a custom backdoor malware called Overstep, which is capable of selectively deleting system logs to obscure its presence and activity.
Security researchers believe the attackers might be using a zero-day vulnerability, or possibly exploiting known flaws like CVE-2021-20038 (a memory corruption bug enabling remote code execution), CVE-2024-38475 (a path traversal issue in Apache that exposes sensitive database files), or CVE-2021-20035 and CVE-2021-20039 (authenticated RCE vulnerabilities previously seen in the wild). There’s also mention of CVE-2025-32819, which could allow credential reset attacks through file deletion.
GTIG, along with Mandiant and SonicWall’s internal response team, has not confirmed exactly how the attackers managed to deploy a reverse shell—something that should not be technically possible under normal device configurations. This shell provides a web-based interface that facilitates the installation of Overstep and potentially gives attackers full control over the compromised appliance.
The motivations behind these breaches are still unclear. Since Overstep deletes key logs, detecting an infection is particularly difficult. However, Google has shared indicators of compromise to help organizations determine if they have been affected. Security teams are strongly advised to investigate the presence of these indicators and consider retiring unsupported hardware from critical infrastructure as part of a proactive defense strategy.
