https://phys.org/news/2018-08-russia-space-station-air-pressure.html

The leak, which was discovered Thursday, was traced to a small hole in one of the Russian Soyuz capsules docked at the station. All members of the space station crew arrive and depart on Soyuz capsules.

Russia's manned space program director, Sergei Krikalev, told state news agency Tass on Friday that the leak was patched with a sealant that is "already proving to be airtight."