Step 1In a small saucepan over medium heat, combine water, brown sugar, granulated sugar, pumpkin, pumpkin pie spice, vanilla, and salt. Bring to a simmer and cook, stirring occasionally, until sugars dissolve and mixture thickens slightly, 5 to 6 minutes (it will thicken more as it cools).
Step 2Let cool completely, then transfer to a resealable container.
Step 3Make Ahead: Syrup can be made 1 week ahead. Store in refrigerator. Shake or whisk before using.