int vorbis_analysis_headerout(vorbis_dsp_state *v,
577                               vorbis_comment *vc,
578                               ogg_packet *op,
579                               ogg_packet *op_comm,
580                               ogg_packet *op_code){
581   int ret=OV_EIMPL;
582   vorbis_info *vi=v->vi;
583   oggpack_buffer opb;
584   private_state *b=v->backend_state;
585 
586   if(!b||vi->channels<=0){
587     ret=OV_EFAULT;
588     goto err_out;
589   }

...

639  err_out:
640   memset(op,0,sizeof(*op));
641   memset(op_comm,0,sizeof(*op_comm));
642   memset(op_code,0,sizeof(*op_code));
643 
644   if(b){
645     oggpack_writeclear(&opb);
646     if(b->header)_ogg_free(b->header);
647     if(b->header1)_ogg_free(b->header1);
648     if(b->header2)_ogg_free(b->header2);
649     b->header=NULL;
650     b->header1=NULL;
651     b->header2=NULL;
652   }

as shown above, if vi->channels<=0 and b!=NULL then func goes to err_out with opb uninitialized, but before calling oggpack_writeclear, it only check if(b),so it will ultimately free a uninitialized memory in oggpack_writeclear:

250 void oggpack_writeclear(oggpack_buffer *b){
 251   if(b->buffer)_ogg_free(b->buffer);
 252   memset(b,0,sizeof(*b));
 253 }

This vul may lead to a DOS or Remote Code Execution in products using libvorbis 1.3.5(latest version).

By the way, I found 8 years ago this function has been found a similar vul :https://bugzilla.mozilla.org/show_bug.cgi?id=550184
while cause of no check of if b=NULL before calling oggpack_writeclear. This time , it is because of incorrect check while no considering if vi->channels<=0.

To reproduce this vul, compile libtheora 1.1.1 libvorbis 1.3.5 libogg 1.3.2 ,then run as below:

╭─root@linux-jiangxin in /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/fuzz 
╰$ gdb ../examples/encoder_example 
GNU gdb (GDB) 7.9
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ../examples/encoder_example...done.

(gdb) run out/Master/crashes/id:000000,sig:06,src:000000,op:flip1,pos:22 xxx.y4m
Starting program: /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example out/Master/crashes/id:000000,sig:06,src:000000,op:flip1,pos:22 xxx.y4m
File out/Master/crashes/id:000000,sig:06,src:000000,op:flip1,pos:22 is 16 bit 0 channel 44100 Hz RIFF WAV audio.
File xxx.y4m is 176x144 29.97 fps mono video.
*** glibc detected *** /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example: munmap_chunk(): invalid pointer: 0x00007fffffffdb30 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x76628)[0x7ffff7864628]
/home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example[0x4a4505]
/home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example[0x504090]
/home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example[0x40535d]
/lib64/libc.so.6(__libc_start_main+0xe6)[0x7ffff780cc36]
/home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example[0x40a039]
======= Memory map: ========
00400000-0063a000 r-xp 00000000 08:08 6452963                            /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example
00839000-0083a000 r--p 00239000 08:08 6452963                            /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example
0083a000-0083b000 rw-p 0023a000 08:08 6452963                            /home/jiangxin/experiment/fuzz/AFL/target/libtheora-1.1.1/examples/encoder_example
0083b000-008e6000 rw-p 00000000 00:00 0                                  [heap]
7ffff75d7000-7ffff75ed000 r-xp 00000000 08:07 155653                     /usr/local/lib64/libgcc_s.so.1
7ffff75ed000-7ffff77ec000 ---p 00016000 08:07 155653                     /usr/local/lib64/libgcc_s.so.1
7ffff77ec000-7ffff77ed000 r--p 00015000 08:07 155653                     /usr/local/lib64/libgcc_s.so.1
7ffff77ed000-7ffff77ee000 rw-p 00016000 08:07 155653                     /usr/local/lib64/libgcc_s.so.1
7ffff77ee000-7ffff795c000 r-xp 00000000 08:07 131081                     /lib64/libc-2.11.3.so
7ffff795c000-7ffff7b5b000 ---p 0016e000 08:07 131081                     /lib64/libc-2.11.3.so
7ffff7b5b000-7ffff7b5f000 r--p 0016d000 08:07 131081                     /lib64/libc-2.11.3.so
7ffff7b5f000-7ffff7b60000 rw-p 00171000 08:07 131081                     /lib64/libc-2.11.3.so
7ffff7b60000-7ffff7b65000 rw-p 00000000 00:00 0 
7ffff7b65000-7ffff7bc0000 r-xp 00000000 08:07 131089                     /lib64/libm-2.11.3.so
7ffff7bc0000-7ffff7dbf000 ---p 0005b000 08:07 131089                     /lib64/libm-2.11.3.so
7ffff7dbf000-7ffff7dc0000 r--p 0005a000 08:07 131089                     /lib64/libm-2.11.3.so
7ffff7dc0000-7ffff7dde000 rw-p 0005b000 08:07 131089                     /lib64/libm-2.11.3.so
7ffff7dde000-7ffff7dfd000 r-xp 00000000 08:07 131074                     /lib64/ld-2.11.3.so
7ffff7f24000-7ffff7fc1000 rw-p 00000000 00:00 0 
7ffff7fc8000-7ffff7ff8000 rw-p 00000000 00:00 0 
7ffff7ff8000-7ffff7ffa000 r--p 00000000 00:00 0                          [vvar]
7ffff7ffa000-7ffff7ffc000 r-xp 00000000 00:00 0                          [vdso]
7ffff7ffc000-7ffff7ffd000 r--p 0001e000 08:07 131074                     /lib64/ld-2.11.3.so
7ffff7ffd000-7ffff7ffe000 rw-p 0001f000 08:07 131074                     /lib64/ld-2.11.3.so
7ffff7ffe000-7ffff7fff000 rw-p 00000000 00:00 0 
7ffffffde000-7ffffffff000 rw-p 00000000 00:00 0                          [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
OggSa8W!۰ہ*theora 
                 	°u0迵@
Program received signal SIGABRT, Aborted.
0x00007ffff7820b55 in raise () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7820b55 in raise () from /lib64/libc.so.6
#1  0x00007ffff7822131 in abort () from /lib64/libc.so.6
#2  0x00007ffff785ee0f in __libc_message () from /lib64/libc.so.6
#3  0x00007ffff7864628 in malloc_printerr () from /lib64/libc.so.6
#4  0x00000000004a4505 in oggpack_writeclear (b=b@entry=0x7fffffffda10) at bitwise.c:251
#5  0x0000000000504090 in vorbis_analysis_headerout (v=v@entry=0x7fffffffdcb0, vc=vc@entry=0x7fffffffdb50, op=op@entry=0x7fffffffdba0, op_comm=op_comm@entry=0x7fffffffdbd0, op_code=op_code@entry=0x7fffffffdc00) at info.c:645
#6  0x000000000040535d in main (argc=<optimized out>, argv=<optimized out>) at encoder_example.c:1688
(gdb) detach
 
files attached:
weird, I can not attach file here, so if you need please contact me for the the crash sample.

This issue has been assigned a CVE number :CVE-2017-14632