Bluebirds boss Neil Warnock is looking to bolster his midfield options during this month's transfer window and he has targeted a move for all-action midfielder Forshaw.
The player's future at Middlesbrough looks uncertain, with the 26-year-old yet to feature for new boss Tony Pulis.
The former Everton man was not named in the squad for the Championship games against Aston Villa and Preston North End and was an unused substitute in last weekend's FA Cup win over Sunderland.
Grant Leadbitter and Jonny Howson have been Pulis's preferred midfield partnership since his arrival at the Riverside, leaving Forshaw down the pecking order.
A number of Championship clubs are monitoring Forshaw's situation and are ready to make a move for the player this month as they look to strengthen their midfield options.
Cardiff are looking to make several signings this month to get their promotion bid back on track after a poor run of form and Warnock feels the Boro man would be a valuable addition to his plans.
However, it remains to be seen if Middlesbrough would be willing to let Forshaw to move to a promotion rival such as Cardiff.