CVE-2021-20110

Due to Manage Engine Asset Explorer Agent 1.0.34 not validating HTTPS
certificates, an attacker on the network can statically configure their IP
address to match the Asset Explorer’s Server IP address. This will allow an
attacker to send a NEWSCAN request to a listening agent on the network as
well as receive the agent’s HTTP request verifying its authtoken. In
httphandler.cpp, the agent reaching out over HTTP is vulnerable to an
Integer Overflow, which can be turned into a Heap Overflow allowing for
remote code execution as NT AUTHORITY/SYSTEM on the agent machine. The
Integer Overflow occurs when receiving POST response from the Manage Engine
server, and the agent calling “HttpQueryInfoW” in order to get the
“Content-Length” size from the incoming POST request. This size is taken,
but multiplied to a larger amount. If an attacker specifies a
Content-Length size of 1073741823 or larger, this integer arithmetic will
wrap the value back around to smaller integer, then calls “calloc” with
this size to allocate memory. The following API “InternetReadFile” will
copy the POST data into this buffer, which will be too small for the
contents, and cause heap overflow.