Cardiff came from two goals down in the last seven minutes to draw 2-2 with the Royals on a freezing cold Monday night at the Madejski Stadium.
But Neil Warnock's promotion-chasing Bluebirds got off to a terrible start when 23-year-old Paterson headed in a hapless opening own goal from Liam Kelly's 16th-minute corner.
Cardiff's boss Warnock was sent to the stands in the second half, but after the game seemed to be in good spirits when joking about his right-back's excellent goalscoring instinct.
"Paterson might as well have left it," he told Sky Sports. "But he took [his own goal] well didn't he?"
The crucial away point for Cardiff means they are now four off leaders Wolves, and hold a four-point advantage over third-placed Bristol City. Reading have moved slightly up the table to 14th.
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