gnucash 2.6.12-1 with Ubuntu 16.04.
This version was installed on May 5th and worked until today when I got an update of metacity (whatever that is). I have reinstalled gnucash, but the error remains the same.
$ gnucash
Found Finance::Quote version 1.38
*** Error in `gnucash': free(): invalid pointer: 0x000056431b7b3960 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x77725)[0x7f5aa25de725]
/lib/x86_64-linux-gnu/libc.so.6(+0x7ff4a)[0x7f5aa25e6f4a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f5aa25eaabc]
...