mp3gain: NULL pointer dereference in sync_buffer (mpglibDBL/interface.c)

Description:
mp3gain is a program to analyze and adjust MP3 files to same volume.

The fuzz was done via the aacgain command-line tool which uses mp3gain which bundles an old-modified version of mpg123 called mpglibDBL.
The upstream project seems to be dead, so the issue wasn’t communicated to them.

The complete ASan output of the issue:

# aacgain -f $FILE
ASAN:DEADLYSIGNAL                                                                                                                                                                                                 
=================================================================                                                                                                                                                 
==23063==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000010 (pc 0x0000008aafe0 bp 0x7ffe06c66450 sp 0x7ffe06c663f0 T0)
    #0 0x8aafdf in sync_buffer /var/tmp/portage/media-sound/aacgain-1.9/work/aacgain-1.9/mp3gain/mpglibDBL/interface.c:393
    #1 0x8ae64c in decodeMP3 /var/tmp/portage/media-sound/aacgain-1.9/work/aacgain-1.9/mp3gain/mpglibDBL/interface.c:665
    #2 0x43e767 in main /var/tmp/portage/media-sound/aacgain-1.9/work/aacgain-1.9/mp3gain/mp3gain.c:2262
    #3 0x7fa37f734680 in __libc_start_main (/lib64/libc.so.6+0x20680)
    #4 0x4426c8 in _start (/usr/bin/aacgain+0x4426c8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /var/tmp/portage/media-sound/aacgain-1.9/work/aacgain-1.9/mp3gain/mpglibDBL/interface.c:393 in sync_buffer
==23063==ABORTING

Affected version:
1.5.2

Fixed version:
N/A

Commit fix:
N/A

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
CVE-2017-14406

Reproducer:
https://github.com/asarubbo/poc/blob/master/00347-aacgain-NULLptr-sync_buffer

Timeline:
2017-08-28: bug discovered
2017-09-08: blog post about the issue
2017-09-13: CVE Assigned

Note:
This bug was found with American Fuzzy Lop.
This bug was identified with bare metal servers donated by Packet. This work is also supported by the Core Infrastructure Initiative.

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mp3gain: NULL pointer dereference in sync_buffer (mpglibDBL/interface.c)