We have observed the following access violation exception in the latest version of Adobe Acrobat Reader DC for Windows, when opening a malformed PDF file:
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First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=707779e0 ebx=25876c38 ecx=052faab8 edx=707703a4 esi=707703d4 edi=25876e34
eip=10e6c29e esp=052fa89c ebp=052fa8a4 iopl=0 nv up ei pl nz ac po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00210212
CoolType!CTInit+0x3913e:
10e6c29e 8902 mov dword ptr [edx],eax ds:002b:707703a4=31a03194
0:000> u @eip-14
CoolType!CTInit+0x3912a:
10e6c28a 8b7d0c mov edi,dword ptr [ebp+0Ch]
10e6c28d 8b571c mov edx,dword ptr [edi+1Ch]
10e6c290 8b7720 mov esi,dword ptr [edi+20h]
10e6c293 035508 add edx,dword ptr [ebp+8]
10e6c296 8b4724 mov eax,dword ptr [edi+24h]
10e6c299 037508 add esi,dword ptr [ebp+8]
10e6c29c 03c6 add eax,esi
10e6c29e 8902 mov dword ptr [edx],eax
0:000> ? poi(edi+1c)
Evaluate expression: -690332 = fff57764
0:000> ? poi(ebp+8)
Evaluate expression: 1887538240 = 70818c40
0:000> !heap -p -a 70818c40
address 70818c40 found in
_DPH_HEAP_ROOT @ bfc1000
in busy allocation ( DPH_HEAP_BLOCK: UserAddr UserSize - VirtAddr VirtSize)
723d3b94: 70818c40 173c0 - 70818000 19000
unknown!fillpattern
0f32a8d0 verifier!AVrfDebugPageHeapAllocate+0x00000240
77f24b26 ntdll!RtlDebugAllocateHeap+0x0000003c
77e7e3e6 ntdll!RtlpAllocateHeap+0x000000f6
77e7cfb7 ntdll!RtlpAllocateHeapInternal+0x000002b7
77e7ccee ntdll!RtlAllocateHeap+0x0000003e
0f48aa2f vrfcore!VfCoreRtlAllocateHeap+0x0000001f
77c2f1f6 ucrtbase!_malloc_base+0x00000026
5fbefc39 AcroRd32!AcroWinMainSandbox+0x00003ec9
10e37991 CoolType!CTInit+0x00004831
10e38e1b CoolType!CTInit+0x00005cbb
10e68870 CoolType!CTInit+0x00035710
10e683dc CoolType!CTInit+0x0003527c
10e67d25 CoolType!CTInit+0x00034bc5
10e65902 CoolType!CTInit+0x000327a2
10e633f2 CoolType!CTInit+0x00030292
10e62719 CoolType!CTInit+0x0002f5b9
10e620e8 CoolType!CTInit+0x0002ef88
10e62000 CoolType!CTInit+0x0002eea0
108f36f1 AGM!AGMInitialize+0x0002a881
0:000> kb
# ChildEBP RetAddr Args to Child
WARNING: Stack unwind information not available. Following frames may be wrong.
00 052fa8a4 10e6bde2 70818c40 25876e34 70818c40 CoolType!CTInit+0x3913e
01 052fa918 10e6bd06 052faab4 052fa9e4 00000001 CoolType!CTInit+0x38c82
02 052fa930 10e6bce7 052faab4 052fa9e4 73330f68 CoolType!CTInit+0x38ba6
03 052fa944 10e6bb4f 052faab4 052fa9e4 73330f68 CoolType!CTInit+0x38b87
04 052fa968 10e6b8b0 052facd8 73330f68 110f7080 CoolType!CTInit+0x389ef
05 052fab08 10e6abf9 73330f68 110f7080 052facd8 CoolType!CTInit+0x38750
06 052fad64 10e65b0c 052fb054 052faddc 00000000 CoolType!CTInit+0x37a99
07 052fb07c 10e633f2 000007c6 00000000 00000000 CoolType!CTInit+0x329ac
08 052fb14c 10e62719 65babff0 00000001 052fb1dc CoolType!CTInit+0x30292
09 052fb964 10e620e8 6aa0a9b4 052fb97c 6aa0a990 CoolType!CTInit+0x2f5b9
0a 052fb9e4 10e62000 6aa0a9b4 6aa0a99c 73fdc4da CoolType!CTInit+0x2ef88
0b 052fba24 108f36f1 7155bd90 6aa0a9b4 6aa0a99c CoolType!CTInit+0x2eea0
0c 052fba38 108e023e 6aa0a99c 108e01d0 331cbd80 AGM!AGMInitialize+0x2a881
0d 052fba4c 108df007 331cbd8c 10d84a18 00000001 AGM!AGMInitialize+0x173ce
0e 052fba84 108f0bcc c1574612 1733a7d0 00000000 AGM!AGMInitialize+0x16197
0f 052fbb4c 0f327c7a 0bfc16cc 052fbb78 0f3291ab AGM!AGMInitialize+0x27d5c
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Notes:
- The crash looks very similar to the one reported in Issue #1891 in June 2019, and fixed in August 2019 as CVE-2019-8042. The stack trace and context are nearly identical. It is possible that this is an unfixed variant of the previous vulnerability.
- Reproduces on Adobe Acrobat Reader DC (2019.012.20040) on Windows 10, with and without PageHeap enabled (more cleanly with PageHeap, though).
- The crash occurs immediately after opening the PDF document, and is caused by an attempt to write data at a negative offset relative to a heap allocation (-690332 in the above case).
- Attached samples: poc[1-4].pdf (crashing files).
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/47769.zip
