We met many crashes like below on iOS 15, it seems multi-thread issue EXC_BAD_ACCESS. We get the dataServiceIdentifier on different threads. Does CTTelephonyNetworkInfo not thread-safe anymore from iOS 15? 0 libobjc.A.dylib _objc_retain 1 CoreTelephony -[CoreTelephonyClientMux cachedValueForSelector:] 2 CoreTelephony -[CoreTelephonyClient(Data) getCurrentDataServiceDescriptorSync:] 3 CoreTelephony -[CTTelephonyNetworkInfo dataServiceIdentifier]