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"): --- cut --- ==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 --- cut --- 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