CVE-2019-3973

Comodo Antivirus versions 11.0.0.6582 and below are vulnerable to Denial of Service affecting CmdGuard.sys via its filter port “cmdServicePort”. A low privileged process can crash CmdVirth.exe to decrease the port’s connection count followed by process hollowing a CmdVirth.exe instance with malicious code to obtain a handle to “cmdServicePort”. Once this occurs, a specially crafted message can be sent to “cmdServicePort” using “FilterSendMessage” API. This can trigger an out-of-bounds write if lpOutBuffer parameter in FilterSendMessage API is near the end of specified buffer bounds. The crash occurs when the driver performs a memset operation which uses a size beyond the size of buffer specified, causing kernel crash.