The X-rated footage allegedly features the 32-year-old reality TV star and her ex-boyfriend Ray J engaged in sexual acts that are even raunchier than their first home video which was leaked in 2007 and eventually released as a DVD entitled Kim Kardashian: Superstar.
A source told the Daily Star newspaper: "It's definitely Kim in the video. And it's even raunchier than her last one. There are all kinds of eye-popping moments."
Kardashian is said to be terrified that the latest sex tape will appear online and cause problems in her relationship with 35-year-old rapper Kanye West.
The source said: "Kim fears this will damage her relationship with Kanye West."
The TV beauty narrowly avoided an embarrassing encounter with R&B singer Ray J, 31, last month when she sneaked out of Prime 112 restaurant in Miami, Florida, to ensure she missed him.
A source explained: "Kim and Kris Jenner posed for pictures in front of the restaurant to allow Kourtney and son Mason to sneak out the side entrance unnoticed.
"And just by a few moments, Kim missed Ray J, who was seen entering the restaurant to meet a large group of friends including boxer Floyd Mayweather."
Kanye West was involved in his own sex tape scandal in September when a 20-minute recording surfaced featuring him and a girl who looks just like Kardashian.