Recursive CTE result is infinite

I have a table "ActionItem" in SQL with ActionItemId, ItemName and ParentActionItemId fields. I am creating a stored procedure which will accept ActionItemId (Id) and display all ActionItem Records that are the children of Id recursively. For this I have used CTE.

ALTER PROCEDURE [dbo].[SSP_ActionItem] 
@ActionItemId int
AS
BEGIN   
WITH ActionItemList AS
(
    --  Anchor
    SELECT ActionItem.ActionItemId,
           ActionItem.ItemName,
           ActionItem.ParentActionItemId 
    FROM ActionItem 
    WHERE ActionItemId=@ActionItemId
    
    UNION ALL
    
    --  Recursive query
    SELECT AIL.ActionItemId,
           AIL.ItemName,
           AIL.ParentActionItemId  
    FROM   ActionItem AS AI INNER JOIN  ActionItemList AS AIL 
    ON AI.ParentActionItemId=AIL.ActionItemId

)
SELECT * FROM ActionItemList
--option (maxrecursion 0)
END 

Table Structure:

   SELECT TOP 1000 [ActionItemId]
    ,[ParentActionItemId]
    ,[ItemName]
    FROM [ActionItem]

This sp returns infinite records.I don't understand where I am going wrong.

Procedure should be:

ALTER PROCEDURE [dbo].[SSP_ActionItem] 
@ActionItemId int
AS
BEGIN   
WITH ActionItemList AS
(
    --  Anchor
    SELECT ActionItem.ActionItemId,
           ActionItem.ItemName,
           ActionItem.ParentActionItemId 
    FROM ActionItem 
    WHERE ActionItemId=@ActionItemId

    UNION ALL

    --  Recursive query
    SELECT AI.ActionItemId,
           AI.ItemName,
           AI.ParentActionItemId  
    FROM   ActionItem AS AI 
    INNER JOIN  ActionItemList AS AIL 
    ON AI.ParentActionItemId=AIL.ActionItemId    
)