CVE-2021-30116

Kaseya VSA before 9.5.7 exposes an unauthenticated client download page (/dl.asp) that leaks agent credentials: the Windows agent stores an Agent_Guid and AgentPassword in KaseyaD.ini, and supplying these to dl.asp via GET parameters authenticates the requester and returns a sessionId cookie. That sessionId can then be used to bypass authentication against services not intended for agent use, and anyone who obtains KaseyaD.ini from a managed endpoint gains enough information to penetrate the VSA installation and its managed clients. On-premises VSA deployments are affected by default, since the vulnerable download page is part of the standard installation. The flaw was exploited in the wild in July 2021 as part of the REvil ransomware campaign against Kaseya VSA, is listed in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) with known ransomware use, and carries a very high EPSS of 85.7%.

What to do: Upgrade Kaseya VSA to 9.5.7 or later per vendor instructions, as required by CISA's KEV catalog. Restrict internet access to the VSA download page (/dl.asp) or disable the agent-login capability there until patched, and review logs for dl.asp GET requests carrying agent credentials (un/pw parameters) or sessionId-based access to services not intended for agent use. Given known ransomware use, treat any unpatched, internet-exposed VSA server as high risk and check managed endpoints for exposed KaseyaD.ini credential material.