Ulreich appeared to hurt his right hand during a session in Qatar, where Bayern are currently enjoying a warm-weather training camp during the Bundesliga’s winter break.
He was taken back to the team hotel on a golf buggy, AFP subsidiary SID reported from Doha. Bayern did not reveal the extent of the injury.
Ulreich has been standing in for the injured Manuel Neuer, and Bayern may therefore need to call on their 36-year-old third choice Tom Starke, who has already played twice this season.
Neuer is recovering from a foot fracture but is walking without crutches again. He stayed in Bavaria along with Thiago Alcantara, who has been out with a muscle tear.
Bayern have made a habit of heading to Qatar for a mid-season break in recent years. They are due to play a friendly against local side Al Ahli on Saturday before returning to Munich on Sunday.
Coach Jupp Heynckes also has Robert Lewandowski (knee) and Mats Hummels (adductor) in the treatment room just now.
However, the arrival of striker Sandro Wagner from Hoffenheim means there may be no need to rush Lewandowski back.
Bayern, who are 11 points clear of Schalke at the top of the table, return to action on Friday, January 12, with a trip to Bayer Leverkusen.