In append_to_verify_fifo_interleaved_ of stream_encoder.c, there is a possible out of bounds write due to a missing bounds check. This could lead to local information disclosure with no additional execution privileges needed.
For Debian 8 jessie, these problems have been fixed in version 1.3.0-3+deb8u2.
We recommend that you upgrade your flac packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/