An exploitable heap overflow vulnerability exists in the JPEG2000 parsing functionality of LEADTOOLS 20.0.2019.3.15. A specially crafted J2K image file can cause an out of bounds write of a null byte in a heap buffer, potentially resulting in code execution. An attack can specially craft a J2K image to trigger this vulnerability.
8.8 - CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE-122: Heap-based Buffer Overflow
LEADTOOLS, according to the website, “is a collection of comprehensive toolkits to integrate document, medical, multimedia, and imaging technologies into desktop, server, tablet, and mobile applications”. It offers prebuilt and portable libraries with an SDK for most platforms (Windows, Linux, Android, etc), that are all geared towards building applications for medical systems.
The module used for this analysis is below: Mapped memory image file: C:\LEADTOOLS 20\Bin\CDLL\win32\lfJ2kU.DLL Image path: C:\LEADTOOLS 20\Bin\CDLL\win32\lfJ2kU.DLL Image name: lfJ2kU.DLL Browse all global symbols functions data Timestamp: Fri Mar 1 07:35:20 2019 (5C795138) CheckSum: 00058242 ImageSize: 0005D000 File version: 184.108.40.206 Product version: 220.127.116.11 File flags: 0 (Mask 3F) File OS: 40004 NT Win32 File type: 2.0 Dll File date: 00000000.00000000 Translations: 0409.04e4
The JPEG2000 file format contains a number of different headers for various parts of the image. The
jp2c header is used for designating a continuous codestream. This codestream has its own set of markers for storing the information in the codestream. The marker containing an image and tile size is 0xFF51. A description of the structure of this marker is below:
Parameter Size (bits) Values SIZ 16 0xFF51 Lsiz 16 4-49 191 Rsiz 16 NA Xsiz 32 1 - (23**2 - 1) Ysiz 32 1 - (23**2 - 1) XOsiz 32 0 - (23**2 - 2) YOsiz 32 0 - (23**2 - 2) XTsiz 32 1 - (23**2 - 1) YTsiz 32 1 - (23**2 - 1) XTOsiz 32 0 - (23**2 - 2) YTOsiz 32 0 - (23**2 - 2) Csiz 16 1 - 16 384 Ssiz(i) 8 NA XRsiz(i) 8 1 - 255 YRsiz(i) 8 1 - 255
When determining the size of the buffer for this image, LEADTOOLS performs the following calculation and allocates a buffer for the structure of the image:
buffer_size = ((Xsiz / XTsiz + 1) * (Ysiz / YTsiz + 1)) * 4
Another codestream marker available in JPEG2000 is SOT, start of tile-part. This marker marks the beginning of a tile-part. Its structure is found below:
Parameter Size (bits) Values SOT 16 0xFF90 Lsot 16 10 Isot 16 0 - 65535 Psot 32 0 - (2**32 - 1) TPsot 8 0 - 255 TNsot 8 0 - 255
One particular field in the SOT is the Isot, which contains the number of tiles. When parsing the SOT, the buffer allocated from the SIZ parsing is referenced by the Isot value. The buffer containing the image structure information is indexed by the Isot value.
lfj2ku+0xa1b3 .text:0000A1B3 mov ecx, [edi] .text:0000A1B5 mov ebx, [ebp+var_18] ; Isot value from file .text:0000A1B8 mov [ebp+var_28], eax .text:0000A1BB mov [ebp+var_34], ecx .text:0000A1BE mov eax, [ecx+0B0h] ; Buffer allocated from SIZ .text:0000A1C4 mov ebx, [eax+ebx*4] ; Value read from indexed buffer
Assuming the read from the buffer is a pointer (and isn’t -1), the assumed structure offset of 0xA7 is checked to be null. If the value is not null, a null is written in its place.
lfj2ku+0xa251 .text:0000A251 cmp byte ptr [ebx+0A7h], 0 ; ebx - buffer .text:0000A258 jz short loc_A27A lfj2ku+0xa25a .text:0000A25A mov ecx, [ebp+var_14] .text:0000A25D mov edx, ebx ; edx - buffer .text:0000A25F call sub_9230 ... lfj2ku+0x923b .text:0000923B mov esi, edx .text:0000923D mov [esp+14h+var_4], ecx .text:00009241 push edi .text:00009242 mov edi, 1 .text:00009247 mov [esp+18h+var_8], edi .text:0000924B mov eax, [esi] .text:0000924D mov byte ptr [esi+0A7h], 0 ; esi - buffer
If the heap has been aligned correctly, it is possible for an attacker set the values of the above calculations to write an arbitrary null out of bounds, potentially leading to code execution.
2019-10-31 - Vendor disclosure
2019-11-06 - Vendor provided timeline for patch
2019-12-05 - Vendor patched
2019-12-10 - Public disclosure
Discovered by Cory Duplantis of Cisco Talos.