That looks like dryer vent duct. IMHO, if you can and are comfortable going on the roof, then look very carefully to see if the vent is allowing the rain in, if so you may need a new exterior vent. If this goes straight up, I would guess a cap came off sometime in the past.
Hope this helps.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
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