The vulnerability is introduced by an insecure change to
LD_LIBRARY_PATH, and environment variable used by ld.so(8) to look for
libraries on a directory other than the standard paths.

Vulnerable code follows:

/usr/bin/mdb-symbolreader line 2:
export LD_LIBRARY_PATH="/usr/lib:${LD_LIBRARY_PATH}"
/usr/bin/mdb line 2:
export LD_LIBRARY_PATH="/usr/lib:${LD_LIBRARY_PATH}"

When there's an empty item on the colon-separated list of
LD_LIBRARY_PATH, ld.so treats it as '.' (i.e. CWD/$PWD.)
If the given script is executed from a directory where a potential,
local, attacker can write files to, there's a chance to exploit this