Submit #752595: ckolivas lrzip 0.651 Memory Corruption

I found a concurrency uaf between the clear_rulist and lzma_decompress_buf functions in the latest master branch 1242aec, and details can be found here: https://github.com/ckolivas/lrzip/issues/262 .

The root cause of this vulnerability is that sinfo->ucthreads may be freed (in clear_rulist) and used (in lzma_decompress_buf) concurrently, leading to a use-after-free.

PoC file:
A crafted PoC is available here: https://github.com/user-attachments/files/21709004/PoC_UAF.zip, please unzip first.

Run Command:

./lrzip -t -p2 ./PoC_UAF
And there is the ASAN report:

=================================================================
==5093==ERROR: AddressSanitizer: heap-use-after-free on address 0x6100000000a0 at pc 0x5604dee94d4e bp 0x7f68f9684c30 sp 0x7f68f9684c20
WRITE of size 8 at 0x6100000000a0 thread T3
#0 0x5604dee94d4d in lzma_decompress_buf /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:562
#1 0x5604dee94d4d in ucompthread /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:1554
#2 0x7f68fca92ac2 in start_thread nptl/pthread_create.c:442
#3 0x7f68fcb2484f (/lib/x86_64-linux-gnu/libc.so.6+0x12684f)

0x6100000000a0 is located 96 bytes inside of 192-byte region [0x610000000040,0x610000000100)
freed by thread T0 here:
#0 0x7f68fd080537 in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:127
#1 0x5604dee7878c in clear_rulist /home/ziiiro/work/eval/vul_repro/lrzip/lrzip.c:786
#2 0x5604dee7effc in decompress_file /home/ziiiro/work/eval/vul_repro/lrzip/lrzip.c:952
#3 0x5604dee74284 in main /home/ziiiro/work/eval/vul_repro/lrzip/main.c:720
#4 0x7f68fca27d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

previously allocated by thread T0 here:
#0 0x7f68fd080a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
#1 0x5604dee9a472 in open_stream_in /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:1101
#2 0x5604dee8ec42 in runzip_chunk /home/ziiiro/work/eval/vul_repro/lrzip/runzip.c:309
#3 0x5604dee8ec42 in runzip_fd /home/ziiiro/work/eval/vul_repro/lrzip/runzip.c:387
#4 0x5604dee7dfe3 in decompress_file /home/ziiiro/work/eval/vul_repro/lrzip/lrzip.c:952
#5 0x5604dee74284 in main /home/ziiiro/work/eval/vul_repro/lrzip/main.c:720
#6 0x7f68fca27d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

Thread T3 created by T0 here:
#0 0x7f68fd024685 in __interceptor_pthread_create ../../../../src/libsanitizer/asan/asan_interceptors.cpp:216
#1 0x5604dee9c8b6 in create_pthread /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:125
#2 0x5604dee9c8b6 in fill_buffer /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:1725
#3 0x5604dee9c8b6 in read_stream /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:1812
#4 0x5604dee8f361 in unzip_literal /home/ziiiro/work/eval/vul_repro/lrzip/runzip.c:162
#5 0x5604dee8f361 in runzip_chunk /home/ziiiro/work/eval/vul_repro/lrzip/runzip.c:325
#6 0x5604dee8f361 in runzip_fd /home/ziiiro/work/eval/vul_repro/lrzip/runzip.c:387
#7 0x5604dee7dfe3 in decompress_file /home/ziiiro/work/eval/vul_repro/lrzip/lrzip.c:952
#8 0x5604dee74284 in main /home/ziiiro/work/eval/vul_repro/lrzip/main.c:720
#9 0x7f68fca27d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

SUMMARY: AddressSanitizer: heap-use-after-free /home/ziiiro/work/eval/vul_repro/lrzip/stream.c:563 in lzma_decompress_buf
Shadow bytes around the buggy address:
0x0c207fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c207fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c207fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c207fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c207fff8000: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
=>0x0c207fff8010: fd fd fd fd[fd]fd fd fd fd fd fd fd fd fd fd fd
0x0c207fff8020: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
0x0c207fff8030: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0c207fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c207fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c207fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
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
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==5093==ABORTING
I believe this concurrency-related memory corruption vulnerability could have serious consequences, for example, with a carefully crafted exploit it could allow arbitrary command execution. So I recommend fixing it as soon as possible.

Thanks

• Quelle: ⚠️ https://github.com/user-attachments/files/21709004/PoC_UAF.zip
• Benutzer: ziiiro (UID 93755)
• Einreichung: 05.02.2026 03:50 (vor 3 Monaten)
• Moderieren: 08.02.2026 09:13 (3 days later)
• Status: Akzeptiert
• VulDB Eintrag: 344926 [ckolivas lrzip bis 0.651 stream.c lzma_decompress_buf Pufferüberlauf]
• Punkte: 20