Talos Vulnerability Report


Accusoft ImageGear TIFF Header count processing out-of-bounds write vulnerability

March 30, 2021
CVE Number



An out-of-bounds write vulnerability exists in the TIFF header count-processing functionality of Accusoft ImageGear 19.8. A specially crafted malformed file can lead to memory corruption. An attacker can provide a malicious file to trigger this vulnerability.

Tested Versions

Accusoft ImageGear 19.8

Product URLs


CVSSv3 Score

8.1 - CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H


CWE-131 - Incorrect Calculation of Buffer Size


The ImageGear library is a document-imaging developer toolkit that offers image conversion, creation, editing, annotation and more. It supports more than 100 formats such as DICOM, PDF, Microsoft Office and others.

There is a vulnerability in the tiff_read_sub_1 function, due to a buffer overflow caused by a missing null check for a size field.
A specially crafted TIFF file can lead to an out-of-bounds write which can result in memory corruption.

Trying to load a malformed TIFF file, we end up in the following situation:

(8920.8408): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=10000021 ebx=0019fc3c ecx=00000000 edx=0adb4ff8 esi=00190001 edi=0adb0ff8
eip=7c1ab972 esp=0019f5f8 ebp=0019f604 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
7c1ab972 66897708        mov     word ptr [edi+8],si      ds:002b:0adb1000=????

When we look at the edi memory allocation we can see the buffer allocated is very small, only 1 byte:

0:000> !heap -p -a edi
    address 0adb0ff8 found in
    _DPH_HEAP_ROOT @ 4ea1000
    in busy allocation (  DPH_HEAP_BLOCK:         UserAddr         UserSize -         VirtAddr         VirtSize)
                                 a993d9c:          adb0ff8                1 -          adb0000             2000
    7c0ea8b0 verifier!AVrfDebugPageHeapAllocate+0x00000240
    774eef8e ntdll!RtlDebugAllocateHeap+0x00000039
    77456150 ntdll!RtlpAllocateHeap+0x000000f0
    774557fe ntdll!RtlpAllocateHeapInternal+0x000003ee
    774553fe ntdll!RtlAllocateHeap+0x0000003e
    7c53dcff MSVCR110!malloc+0x00000049
    7c1b61de igCore19d!AF_memm_alloc+0x0000001e
    7c2c6ff0 igCore19d!IG_mpi_page_set+0x0010b2a0
    7c2c6f9a igCore19d!IG_mpi_page_set+0x0010b24a
    7c2cc0a3 igCore19d!IG_mpi_page_set+0x00110353
    7c2c604b igCore19d!IG_mpi_page_set+0x0010a2fb
    7c1910d9 igCore19d!IG_image_savelist_get+0x00000b29
    7c1d0557 igCore19d!IG_mpi_page_set+0x00014807
    7c1cfeb9 igCore19d!IG_mpi_page_set+0x00014169
    7c165777 igCore19d!IG_load_file+0x00000047
    004021f9 Fuzzme!fuzzme+0x00000019
    00402504 Fuzzme!fuzzme+0x00000324
    0040666d Fuzzme!fuzzme+0x0000448d
    7719fa29 KERNEL32!BaseThreadInitThunk+0x00000019
    774775f4 ntdll!__RtlUserThreadStart+0x0000002f
    774775c4 ntdll!_RtlUserThreadStart+0x0000001b

The crash is happening in the following pseudo code of the function init_io_buffer in LINE7 as edi contains the io_buff pointer:

LINE1  dword init_io_buffer(mys_table_function *mys_table_function_obj,uint kind_of_heap,io_buffer *io_buff
LINE2                      ,int size_to_allocate,short constant_1)
LINE3  {
LINE5    set_into_param2_endian_type(mys_table_function_obj,&io_buff->endian_type);
LINE6    io_buff->ptr_mys_table_function = mys_table_function_obj;
LINE7    io_buff->field_0x8 = constant_1;
LINE8    io_buff->kind_of_heap = kind_of_heap;
LINE9    io_buff->buffer_size = size_to_allocate;
LINE10   io_buff->field_0xc = 0;
LINE11   [...]
LINE12 }

The root cause is coming from the caller function tiff_read_sub_1 which is responsible for the allocation of io_buff. The pseudo-code of tiff_read_sub_1:

LINE14 void tiff_read_sub_1(mys_table_function *mys_table_function_obj,uint kind_of_heap,
LINE15                     mys_tags_data *tags_data,undefined4 param_4,HIGDIBINFO Obj_HIGDIBINFO,
LINE16                     short *param_6)
LINE17 {
LINE18   io_buffer *ptr_io_buff;
LINE19   byte **dst;
LINE20   byte **error_message;
LINE21   size_t size;
LINE22   BYTE *pBVar1;
LINE23   int iVar2;
LINE24   dword dVar3;
LINE25   byte *pbVar4;
LINE26   int iVar5;
LINE27   int iVar6;
LINE28   io_buffer *piVar7;
LINE29   uint uVar8;
LINE31   undefined4 uVar10;
LINE32   int local_28;
LINE33   byte *local_24;
LINE34   byte *local_20;
LINE35   int *local_1c;
LINE36   int local_18;
LINE37   uint size_to_allocate;
LINE38   uint local_c;
LINE40   local_20 = NULL;
LINE41   size_to_allocate = 0;
LINE42   local_c = 0;
LINE43   local_24 = NULL;
LINE44   local_1c = NULL;
LINE45   ptr_io_buff = (io_buffer *)
LINE46                 AF_memm_alloc(kind_of_heap,
LINE47                               (uint)*(ushort *)&tags_data->SamplesPerPixel_Or_CountValue * 0x34,
LINE48                               (dword)"..\\..\\..\\..\\Common\\Formats\\tifread.c");
LINE49   if (ptr_io_buff == NULL) {
LINE50     AF_err_record_set("..\\..\\..\\..\\Common\\Formats\\tifread.c",0x178b,-1000,0,0,0,NULL);
LINE51     AF_error_check();
LINE52     return;
LINE53   }
LINE54  [...]   
LINE55 LAB_101771f6:
LINE56           dVar3 = init_io_buffer(mys_table_function_obj,kind_of_heap,ptr_io_buff,
LINE57                                  (int)*error_message * 5,1);
LINE58  [...]
LINE59 }

The tiff_read_sub_1 function starts by allocating in LINE45 the memory buffer which can be overwritten represented by the variable ptr_io_buff . The size used for the memory allocation is directly read from the file, and corresponds to the count value of TIFF tags ImageWidth or ImageLength. By default this value is set to 1 according to documentation. There is no check against the buffer size before the call to the init_io_buffer in LINE56. The function AF_memm_alloc is a wrapper to malloc, thus when passing a null value it returns a buffer of one byte.
So, when calling init_io_buffer, that function assumes the ptr_io_buff points to a properly allocated io_buffer structure, and initializes some of its fields by writing inside the pointed structure. Since in our case the buffer is only 1 byte long, most of the assignments happening inside that function (e.g. LINE7 and LINE10 are writing constant values 1 and 0 respectively) are out-of-bounds heap writes which lead to memory corruption and possibly code execution.

Crash Information

0:000> !analyze -v
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *


    Key  : AV.Fault
    Value: Write

    Key  : Analysis.CPU.mSec
    Value: 1249

    Key  : Analysis.DebugAnalysisProvider.CPP
    Value: Create: 8007007e on DESKTOP-4DAOCFH

    Key  : Analysis.DebugData
    Value: CreateObject

    Key  : Analysis.DebugModel
    Value: CreateObject

    Key  : Analysis.Elapsed.mSec
    Value: 9397

    Key  : Analysis.Memory.CommitPeak.Mb
    Value: 72

    Key  : Analysis.System
    Value: CreateObject

    Key  : Timeline.OS.Boot.DeltaSec
    Value: 261278

    Key  : Timeline.Process.Start.DeltaSec
    Value: 2029

    Key  : WER.OS.Branch
    Value: vb_release

    Key  : WER.OS.Timestamp
    Value: 2019-12-06T14:06:00Z

    Key  : WER.OS.Version
    Value: 10.0.19041.1

    Key  : WER.Process.Version






ExceptionAddress: 7c1ab972 (igCore19d!IG_cpm_profiles_reset+0x00010b62)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000001
   Parameter[1]: 0adb1000
Attempt to write to address 0adb1000


PROCESS_NAME:  Fuzzme.exe

WRITE_ADDRESS:  0adb1000 

ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s.




WARNING: Stack unwind information not available. Following frames may be wrong.
0019f604 7c2c7648     0019fc3c 10000021 0adb0ff8 igCore19d!IG_cpm_profiles_reset+0x10b62
0019f650 7c2c6f9a     0019fc3c 10000021 0adb4ff8 igCore19d!IG_mpi_page_set+0x10b8f8
0019f678 7c2cc0a3     0019fc3c 10000021 0019f6d0 igCore19d!IG_mpi_page_set+0x10b24a
0019f6a0 7c2c604b     0019fc3c 10000021 0ab7dd68 igCore19d!IG_mpi_page_set+0x110353
0019fbb4 7c1910d9     0019fc3c 0ab7dd68 00000001 igCore19d!IG_mpi_page_set+0x10a2fb
0019fbec 7c1d0557     00000000 0ab7dd68 0019fc3c igCore19d!IG_image_savelist_get+0xb29
0019fe68 7c1cfeb9     00000000 05295f80 00000001 igCore19d!IG_mpi_page_set+0x14807
0019fe88 7c165777     00000000 05295f80 00000001 igCore19d!IG_mpi_page_set+0x14169
0019fea8 004021f9     05295f80 0019febc 00000001 igCore19d!IG_load_file+0x47
0019fec0 00402504     05295f80 05293fc0 051e3f28 Fuzzme!fuzzme+0x19
0019ff28 0040666d     00000005 051daee8 051e3f28 Fuzzme!fuzzme+0x324
0019ff70 7719fa29     00268000 7719fa10 0019ffdc Fuzzme!fuzzme+0x448d
0019ff80 774775f4     00268000 0f9e4eaf 00000000 KERNEL32!BaseThreadInitThunk+0x19
0019ffdc 774775c4     ffffffff 77497336 00000000 ntdll!__RtlUserThreadStart+0x2f
0019ffec 00000000     004066f5 00268000 00000000 ntdll!_RtlUserThreadStart+0x1b

STACK_COMMAND:  ~0s ; .cxr ; kb

SYMBOL_NAME:  igCore19d!IG_cpm_profiles_reset+10b62

MODULE_NAME: igCore19d

IMAGE_NAME:  igCore19d.dll

FAILURE_BUCKET_ID:  INVALID_POINTER_WRITE_AVRF_c0000005_igCore19d.dll!IG_cpm_profiles_reset

OS_VERSION:  10.0.19041.1

BUILDLAB_STR:  vb_release


OSNAME:  Windows 10


FAILURE_ID_HASH:  {749e662e-5382-aab8-f02d-cecd73653ce6}

Followup:     MachineOwner


2021-01-15 - Vendor Disclosure
2021-02-05 - Vendor Patched
2021-03-30 - Public Release


Discovered by Emmanuel Tacheau of Cisco Talos.