CVE-2021-20038

SonicWall SMA 100 series secure remote-access appliances contain an unauthenticated stack-based buffer overflow (CWE-121) in the appliance's network-facing interface, triggered by crafted requests sent to the device without any credentials. A remote attacker who triggers the overflow can execute arbitrary code on the appliance with the privileges of the affected service, gaining a foothold on an internet-facing VPN gateway that typically sits at the network edge. Any organization running an SMA 100 series appliance is affected, and because these appliances provide remote access to corporate networks, compromise can expose entire internal environments. Exploitation is confirmed in the wild: the flaw was added to CISA KEV on 2022-01-28 with known ransomware use, and EPSS assigns a 99.9% probability of exploitation within 30 days (100th percentile). No public proof-of-concept is catalogued in the provided data, but the KEV listing and EPSS score indicate active attacker interest.

What to do: Upgrade SMA 100 series appliances to firmware 10.0.7.2 or later per SonicWall's instructions, as required by the CISA KEV listing. Until patched, restrict internet exposure of the SMA portal and management interface to trusted sources where feasible. Because ransomware operators are known to exploit this flaw, review appliance logs for signs of compromise and monitor for unexpected account creation or traffic after patching.