Source: https://code.google.com/p/google-security-research/issues/detail?id=636
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 --html /path/to/file"):
--- cut ---
==26202==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62100001c900 at pc 0x0000008073f9 bp 0x7ffd791c7f90 sp 0x7ffd791c7f88
READ of size 1 at 0x62100001c900 thread T0
#0 0x8073f8 in htmlCurrentChar libxml2-2.9.3/HTMLparser.c:439:6
#1 0x80ee62 in htmlParseCharDataInternal libxml2-2.9.3/HTMLparser.c:3011:8
#2 0x821b85 in htmlParseCharData libxml2-2.9.3/HTMLparser.c:3061:5
#3 0x7df875 in htmlParseContentInternal libxml2-2.9.3/HTMLparser.c:4634:3
#4 0x7e2f0f in htmlParseDocument libxml2-2.9.3/HTMLparser.c:4769:5
#5 0x802c55 in htmlDoRead libxml2-2.9.3/HTMLparser.c:6741:5
#6 0x8030b6 in htmlReadFile libxml2-2.9.3/HTMLparser.c:6799:13
#7 0x4f47a5 in parseAndPrintFile libxml2-2.9.3/xmllint.c:2248:8
#8 0x4ebe8f in main libxml2-2.9.3/xmllint.c:3759:7
0x62100001c900 is located 0 bytes to the right of 4096-byte region [0x62100001b900,0x62100001c900)
allocated by thread T0 here:
#0 0x4b8b68 in malloc llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:40
#1 0xa01a0c in xmlBufCreate libxml2-2.9.3/buf.c:137:32
#2 0x550aca in xmlSwitchInputEncodingInt libxml2-2.9.3/parserInternals.c:1205:34
#3 0x54f5ce in xmlSwitchToEncodingInt libxml2-2.9.3/parserInternals.c:1281:12
#4 0x54f278 in xmlSwitchEncoding libxml2-2.9.3/parserInternals.c:1101:11
#5 0x808eea in htmlCurrentChar libxml2-2.9.3/HTMLparser.c:518:13
#6 0x804a38 in htmlParseNameComplex libxml2-2.9.3/HTMLparser.c:2496:9
#7 0x7cc29d in htmlParseName libxml2-2.9.3/HTMLparser.c:2483:12
#8 0x7ec211 in htmlParseDocTypeDecl libxml2-2.9.3/HTMLparser.c:3424:12
#9 0x7debf4 in htmlParseContentInternal libxml2-2.9.3/HTMLparser.c:4585:3
#10 0x7e2f0f in htmlParseDocument libxml2-2.9.3/HTMLparser.c:4769:5
#11 0x802c55 in htmlDoRead libxml2-2.9.3/HTMLparser.c:6741:5
#12 0x8030b6 in htmlReadFile libxml2-2.9.3/HTMLparser.c:6799:13
#13 0x4f47a5 in parseAndPrintFile libxml2-2.9.3/xmllint.c:2248:8
#14 0x4ebe8f in main libxml2-2.9.3/xmllint.c:3759:7
SUMMARY: AddressSanitizer: heap-buffer-overflow libxml2-2.9.3/HTMLparser.c:439:6 in htmlCurrentChar
Shadow bytes around the buggy address:
0x0c427fffb8d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c427fffb8e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c427fffb8f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c427fffb900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c427fffb910: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c427fffb920:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c427fffb930: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c427fffb940: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c427fffb950: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c427fffb960: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c427fffb970: 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
==26202==ABORTING
--- cut ---
The crash was reported at https://bugzilla.gnome.org/show_bug.cgi?id=758606. Attached is an XML file which triggers the crash.
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39494.zip
