Source: https://code.google.com/p/google-security-research/issues/detail?id=639
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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==4210==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6290000051ff at pc 0x000000533c8f bp 0x7ffdb38c4830 sp 0x7ffdb38c4828
READ of size 1 at 0x6290000051ff thread T0
#0 0x533c8e in xmlParserPrintFileContextInternal libxml2-2.9.3/error.c:192:6
#1 0x54088a in xmlReportError libxml2-2.9.3/error.c:406:9
#2 0x53884f in __xmlRaiseError libxml2-2.9.3/error.c:633:2
#3 0x56f0ec in xmlFatalErr libxml2-2.9.3/parser.c:540:5
#4 0x569c98 in xmlGROW libxml2-2.9.3/parser.c:2077:9
#5 0x62bcb3 in xmlParseEndTag2 libxml2-2.9.3/parser.c:9846:5
#6 0x61d620 in xmlParseElement libxml2-2.9.3/parser.c:10238:2
#7 0x63be9b in xmlParseDocument libxml2-2.9.3/parser.c:10912:2
#8 0x672b74 in xmlDoRead libxml2-2.9.3/parser.c:15390:5
#9 0x673041 in xmlReadFile libxml2-2.9.3/parser.c:15452:13
#10 0x4f5b60 in parseAndPrintFile libxml2-2.9.3/xmllint.c:2401:9
#11 0x4ebe8f in main libxml2-2.9.3/xmllint.c:3759:7
0x6290000051ff is located 1 bytes to the left of 16384-byte region [0x629000005200,0x629000009200)
allocated by thread T0 here:
#0 0x4b8b68 in malloc llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:40
#1 0x7f4df5219729 (/lib/x86_64-linux-gnu/libz.so.1+0xf729)
SUMMARY: AddressSanitizer: heap-buffer-overflow libxml2-2.9.3/error.c:192:6 in xmlParserPrintFileContextInternal
Shadow bytes around the buggy address:
0x0c527fff89e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff89f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8a00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8a10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c527fff8a20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c527fff8a30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa]
0x0c527fff8a40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c527fff8a50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c527fff8a60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c527fff8a70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c527fff8a80: 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
Left alloca redzone: ca
Right alloca redzone: cb
==4210==ABORTING
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The crash was reported at https://bugzilla.gnome.org/show_bug.cgi?id=758588. Attached is an XML file which triggers the crash.
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39493.zip
