Headline
CVE-2020-21596: global buffer overflow in decode_CABAC_bit when decoding file · Issue #236 · strukturag/libde265
libde265 v1.0.4 contains a global buffer overflow in the decode_CABAC_bit function, which can be exploited via a crafted a file.
global buffer overflow in decode_CABAC_bit when decoding file
I found some problems during fuzzing
Test Version
dev version, git clone https://github.com/strukturag/libde265
Test Environment
root@ubuntu:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.6 LTS
Release: 16.04
Codename: xenial
root@ubuntu:# uname -a
Linux ubuntu 4.15.0-45-generic #4816.04.1-Ubuntu SMP Tue Jan 29 18:03:48 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Test Configure
./configure
configure: ---------------------------------------
configure: Building dec265 example: yes
configure: Building sherlock265 example: no
configure: Building encoder: yes
configure: ---------------------------------------
Test Program
dec265 [infile]
Asan Output
root@ubuntu:~# ./dec265 libde265-decode_CABAC_bit-overflow.crash
WARNING: CTB outside of image area (concealing stream error...)
WARNING: end_of_sub_stream_one_bit not set to 1 when it should be
WARNING: slice header invalid
=================================================================
==58539==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000054625f at pc 0x0000004fc1cf bp 0x7fffa287c990 sp 0x7fffa287c980
READ of size 1 at 0x00000054625f thread T0
#0 0x4fc1ce in decode_CABAC_bit(CABAC_decoder*, context_model*) /root/src/libde265/libde265/cabac.cc:180
#1 0x46fca1 in decode_cu_skip_flag /root/src/libde265/libde265/slice.cc:1679
#2 0x4797c7 in read_coding_unit(thread_context*, int, int, int, int) /root/src/libde265/libde265/slice.cc:4289
#3 0x47b6fe in read_coding_quadtree(thread_context*, int, int, int, int) /root/src/libde265/libde265/slice.cc:4647
#4 0x47b53f in read_coding_quadtree(thread_context*, int, int, int, int) /root/src/libde265/libde265/slice.cc:4630
#5 0x47338a in read_coding_tree_unit(thread_context*) /root/src/libde265/libde265/slice.cc:2861
#6 0x47beb1 in decode_substream(thread_context*, bool, bool) /root/src/libde265/libde265/slice.cc:4736
#7 0x47db9f in read_slice_segment_data(thread_context*) /root/src/libde265/libde265/slice.cc:5049
#8 0x40bf17 in decoder_context::decode_slice_unit_sequential(image_unit*, slice_unit*) /root/src/libde265/libde265/decctx.cc:843
#9 0x40c6d7 in decoder_context::decode_slice_unit_parallel(image_unit*, slice_unit*) /root/src/libde265/libde265/decctx.cc:945
#10 0x40b589 in decoder_context::decode_some(bool*) /root/src/libde265/libde265/decctx.cc:730
#11 0x40b2f2 in decoder_context::read_slice_NAL(bitreader&, NAL_unit*, nal_header&) /root/src/libde265/libde265/decctx.cc:688
#12 0x40dbb3 in decoder_context::decode_NAL(NAL_unit*) /root/src/libde265/libde265/decctx.cc:1230
#13 0x40e17b in decoder_context::decode(int*) /root/src/libde265/libde265/decctx.cc:1318
#14 0x405a61 in de265_decode /root/src/libde265/libde265/de265.cc:346
#15 0x404972 in main /root/src/libde265/dec265/dec265.cc:764
#16 0x7f83f76d982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#17 0x402b28 in _start (/root/dec265+0x402b28)
0x00000054625f is located 31 bytes to the right of global variable 'next_state_MPS' defined in 'cabac.cc:112:22' (0x546200) of size 64
0x00000054625f is located 1 bytes to the left of global variable 'next_state_LPS' defined in 'cabac.cc:120:22' (0x546260) of size 64
SUMMARY: AddressSanitizer: global-buffer-overflow /root/src/libde265/libde265/cabac.cc:180 decode_CABAC_bit(CABAC_decoder*, context_model*)
Shadow bytes around the buggy address:
0x0000800a0bf0: 00 00 00 01 f9 f9 f9 f9 00 00 00 00 00 02 f9 f9
0x0000800a0c00: f9 f9 f9 f9 00 00 00 00 00 00 00 00 01 f9 f9 f9
0x0000800a0c10: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
0x0000800a0c20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0000800a0c30: 00 00 00 00 f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9
=>0x0000800a0c40: 00 00 00 00 00 00 00 00 f9 f9 f9[f9]00 00 00 00
0x0000800a0c50: 00 00 00 00 f9 f9 f9 f9 00 01 f9 f9 f9 f9 f9 f9
0x0000800a0c60: 00 04 f9 f9 f9 f9 f9 f9 00 00 00 f9 f9 f9 f9 f9
0x0000800a0c70: 00 01 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
0x0000800a0c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0000800a0c90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
==58539==ABORTING
POC file
libde265-decode_CABAC_bit-overflow.zip
password: leon.zhao.7
CREDIT
Zhao Liang, Huawei Weiran Labs
Related news
Gentoo Linux Security Advisory 202408-20 - Multiple vulnerabilities have been discovered in libde265, the worst of which could lead to arbitrary code execution. Versions greater than or equal to 1.0.11 are affected.
Ubuntu Security Notice 6617-1 - It was discovered that libde265 could be made to write out of bounds. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly use this issue to cause a denial of service or execute arbitrary code. This issue only affected Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. It was discovered that libde265 could be made to write out of bounds. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly use this issue to cause a denial of service or execute arbitrary code.
Debian Linux Security Advisory 5346-1 - Multiple security issues were discovered in libde265, an implementation of the H.265 video codec which may result in denial of service and potentially the execution of arbitrary code if a malformed media file is processed.