QlikView – ‘.qvw’ File Remote Integer Overflow
source: https://www.securityfocus.com/bid/58463/info QlikView is prone to a remote integer-overflow vulnerability. Successful attacks will allow attackers to execute arbitrary code within the context of the application. Failed exploit attempts will result in a denial-of-service condition. QlikView 11.00 SR2 is vulnerable; other versions may also be affected. Vulnerability details: ---------------------- The .qvw file is divided into several sections with a specified delimiter. Among others, there is a parameter which is responsible for defining the section length. On the hex listing below it's the DWORD A4 00 00 00 (address 315EF) 000315B0: 00 00 01 00-00 00 0E 23-23 23 23 23-23 23 23 23 000315C0: 23 23 23 23-23 01 2E 00-00 00 00 00-00 00 00 00 000315D0: 00 00 00 00-00 00 00 00-00 00 00 00-00 00 00 03 000315E0: 00 00 00 00-00 00 00 90-02 00 00 00-00 04 00 A4 000315F0: 00 00 00 78-9C 3D CC CB-4A 02 50 14-86 D1 1F 47 If by any reasons the value is bigger than the actual size of the section, an error is handled by a C++ EH and a message "Document failed to load" is shown. The check condition can be seen here: .text:00D6BD66 mov eax, [edi+28h] .text:00D6BD69 mov ebx, [eax] ; here is the length parameter .text:00D6BD6B add eax, 4 .text:00D6BD6E mov [edi+28h], eax .text:00D6BD71 cmp ebx, [ebp+var_14] .text:00D6BD74 jg loc_D6BBAC ; check if the parameter value is bigger than actual length However, the comparison operates with a signed number and doesn't check if it's less than zero. In other words, if an attacker supplies a DWORD bigger than 0x80000000, the jump will not be taken (as the number will be considered as negative), causing an integer overflow. After that, the length parameter is used as the DstSize argument to the CArchive::Read function: .text:00D6BD7A mov eax, [ebp+Dst] .text:00D6BD7D push ebx ; DstSize .text:00D6BD7E push eax ; Dst .text:00D6BD7F mov ecx, edi .text:00D6BD81 call ?Read () CArchive@@QAEIPAXI () Z ; CArchive::Read(void *,uint) A large amount of data is read. It is used later to fill the created Archive whose size is 0x8000: .text:00B26207 push 0 .text:00B26209 push 8000h .text:00B2620E push 1 .text:00B26210 lea eax, [ebp+var_60] .text:00B26213 push eax .text:00B26214 lea ecx, [ebp+var_A8] .text:00B2621A call ??0CArchive@@QAE () PAVCFile@@IHPAX () Z ; CArchive::CArchive(CFile *,uint,int,void *) This results in the controlled address being overwritten with the controlled value. .text:009F3092 mov ecx, [esi] .text:009F3094 mov edx, [esi+4] .text:009F3097 mov [ecx+4], edx ; here the error occurs; .text:009F3097 ; trying to write at non-existing address An extract from a debugger with the occurence of the error is presented below. eax=04735f14 ebx=00000000 ecx=bbbbbbb7 edx=aaaaaaa6 esi=04b2fbc0 edi=04735f10 eip=01723097 esp=003527f8 ebp=00352818 iopl=0 nv up ei pl nz ac pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010216 Qv+0x5f3097: 01723097 895104 mov dword ptr [ecx+4],edx ds:002b:bbbbbbbb=???????? |