Source: https://code.google.com/p/google-security-research/issues/detail?id=638
The following crash due to a heap-based out-of-bounds memory read can be observed in an ASAN build of latest stable libxml2 (2.9.3, released 4 days ago), by feeding a malformed file to xmllint ("$ ./xmllint /path/to/file"):
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==4588==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6290000049e6 at pc 0x00000062b643 bp 0x7ffffa00f570 sp 0x7ffffa00f568
READ of size 1 at 0x6290000049e6 thread T0
#0 0x62b642 in xmlParseEndTag2 libxml2-2.9.3/parser.c:9828:13
#1 0x61d620 in xmlParseElement libxml2-2.9.3/parser.c:10238:2
#2 0x618dac in xmlParseContent libxml2-2.9.3/parser.c:10042:6
#3 0x61cc7c in xmlParseElement libxml2-2.9.3/parser.c:10215:5
#4 0x618dac in xmlParseContent libxml2-2.9.3/parser.c:10042:6
#5 0x61cc7c in xmlParseElement libxml2-2.9.3/parser.c:10215:5
#6 0x63be9b in xmlParseDocument libxml2-2.9.3/parser.c:10912:2
#7 0x672b74 in xmlDoRead libxml2-2.9.3/parser.c:15390:5
#8 0x673041 in xmlReadFile libxml2-2.9.3/parser.c:15452:13
#9 0x4f5b60 in parseAndPrintFile libxml2-2.9.3/xmllint.c:2401:9
#10 0x4ebe8f in main libxml2-2.9.3/xmllint.c:3759:7
0x6290000049e6 is located 2018 bytes to the right of 16388-byte region [0x629000000200,0x629000004204)
allocated by thread T0 here:
#0 0x4b8ef0 in realloc llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:61
#1 0xa079a5 in xmlBufGrowInternal libxml2-2.9.3/buf.c:486:23
#2 0xa06722 in xmlBufGrow libxml2-2.9.3/buf.c:515:11
#3 0x72fef4 in xmlParserInputBufferGrow libxml2-2.9.3/xmlIO.c:3326:9
#4 0x543b22 in xmlParserInputGrow libxml2-2.9.3/parserInternals.c:320:8
#5 0x569d10 in xmlGROW libxml2-2.9.3/parser.c:2081:5
#6 0x68208d in xmlParseNCNameComplex libxml2-2.9.3/parser.c:3499:6
#7 0x68136d in xmlParseNCName libxml2-2.9.3/parser.c:3591:12
#8 0x67d282 in xmlParseQName libxml2-2.9.3/parser.c:8859:9
#9 0x61f04d in xmlParseStartTag2 libxml2-2.9.3/parser.c:9381:17
#10 0x61a626 in xmlParseElement libxml2-2.9.3/parser.c:10129:16
#11 0x618dac in xmlParseContent libxml2-2.9.3/parser.c:10042:6
#12 0x61cc7c in xmlParseElement libxml2-2.9.3/parser.c:10215:5
#13 0x618dac in xmlParseContent libxml2-2.9.3/parser.c:10042:6
#14 0x61cc7c in xmlParseElement libxml2-2.9.3/parser.c:10215:5
#15 0x63be9b in xmlParseDocument libxml2-2.9.3/parser.c:10912:2
#16 0x672b74 in xmlDoRead libxml2-2.9.3/parser.c:15390:5
#17 0x673041 in xmlReadFile libxml2-2.9.3/parser.c:15452:13
#18 0x4f5b60 in parseAndPrintFile libxml2-2.9.3/xmllint.c:2401:9
#19 0x4ebe8f in main libxml2-2.9.3/xmllint.c:3759:7
SUMMARY: AddressSanitizer: heap-buffer-overflow libxml2-2.9.3/parser.c:9828:13 in xmlParseEndTag2
Shadow bytes around the buggy address:
0x0c527fff88e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff88f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8900: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8910: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8920: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c527fff8930: fa fa fa fa fa fa fa fa fa fa fa fa[fa]fa fa fa
0x0c527fff8940: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8950: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8960: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8970: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8980: 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
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
Left alloca redzone: ca
Right alloca redzone: cb
==4588==ABORTING
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The crash was reported at https://bugzilla.gnome.org/show_bug.cgi?id=758589. Attached is an XML file which triggers the crash.
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39492.zip
