Created attachment 14087 [details]
Reproducers.

Build Information:
Wireshark git master.
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The following crash due to a heap-based out-of-bounds read can be observed in an ASAN build of Wireshark (current git master), by feeding a malformed file to tshark ("$ ./tshark -nVxr /path/to/file"):

Attached are three files which trigger the crash.

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==6473==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61b00001335c at pc 0x7f391e585d1e bp 0x7ffc0ff625c0 sp 0x7ffc0ff625b8
READ of size 1 at 0x61b00001335c thread T0
    #0 0x7f391e585d1d in infer_pkt_encap wireshark/wiretap/ngsniffer.c:1767:27
    #1 0x7f391e582ac7 in fix_pseudo_header wireshark/wiretap/ngsniffer.c:1805:11
    #2 0x7f391e57d07e in ngsniffer_process_record wireshark/wiretap/ngsniffer.c:1299:20
    #3 0x7f391e576418 in ngsniffer_read wireshark/wiretap/ngsniffer.c:1034:9
    #4 0x7f391e62429b in wtap_read wireshark/wiretap/wtap.c:1309:7
    #5 0x51f7ea in load_cap_file wireshark/tshark.c:3479:12
    #6 0x515daf in main wireshark/tshark.c:2197:13

0x61b00001335c is located 0 bytes to the right of 1500-byte region [0x61b000012d80,0x61b00001335c)
allocated by thread T0 here:
    #0 0x4c0bc8 in malloc llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:40
    #1 0x7f390a251610 in g_malloc (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x4e610)
    #2 0x7f391e48d0e5 in wtap_open_offline wireshark/wiretap/file_access.c:1105:2
    #3 0x51bd1d in cf_open wireshark/tshark.c:4195:9
    #4 0x51584e in main wireshark/tshark.c:2188:9

SUMMARY: AddressSanitizer: heap-buffer-overflow wireshark/wiretap/ngsniffer.c:1767:27 in infer_pkt_encap
Shadow bytes around the buggy address:
  0x0c367fffa610: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa620: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa630: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa640: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa650: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c367fffa660: 00 00 00 00 00 00 00 00 00 00 00[04]fa fa fa fa
  0x0c367fffa670: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c367fffa680: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c367fffa690: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa6a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c367fffa6b0: 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
==6473==ABORTING
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This bug is subject to a 90 day disclosure deadline. If 90 days elapse without a broadly available patch, then the bug report will automatically become visible to the public.