Fix out-of-bounds memory access in bit.

* mpi/mpi.c (mp_bit): If the digit index is beyond
the available digits in the number, report MP_NO rather than
accessing undefined digit material or beyond the array
entirely.

1 files changed, 1 insertions, 1 deletions

diff --git a/mpi/mpi.c b/mpi/mpi.c
index cb6567a5..178b5fee 100644
--- a/mpi/mpi.c
+++ b/mpi/mpi.c
@@ -2781,7 +2781,7 @@ mp_err mp_bit(mp_int *a, mp_digit bit)
     a = &tmp;
   }
 
-  return (DIGITS(a)[digit] & mask) != 0 ? MP_YES : MP_NO;
+  return (digit < USED(a) && (DIGITS(a)[digit] & mask) != 0) ? MP_YES : MP_NO;
 }
 
 mp_err mp_to_double(mp_int *mp, double *d)