Out-of-bounds read

Incorrect values read from a different memory region will cause incorrect computations. Out-of-bounds read from a buffer
/src/mongo/db/storage/key_string.cpp:693: OVERRUN 115379 Function call "mongo::countLeadingZeros64(integerPart << 1)" may return 64.
/src/mongo/db/storage/key_string.cpp:693: OVERRUN 115379 Assigning: "fractionalBytes" = "mongo::countLeadingZeros64(integerPart << 1) / 8". The value of "fractionalBytes" is now 8.
/src/mongo/db/storage/key_string.cpp:700: OVERRUN 115379 Overrunning array "mongo::KeyString::<unnamed>::kPow256" of 8 8-byte elements at element index 8 (byte offset 71) using index "fractionalBytes" (which evaluates to 8).