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Regarding Microsoft srv2.sys SMB2.0 NEGOTIATE BSOD

[Original Advisory ] Lauren Gaffié

Hi all,

Just for the records since the vulnerability is not only a DoS as stated
initially. Below are the technical details I found while verifying the flaw.

* This vulnerability is not only a BSOD flaw. It allows remote code
execution. The execution of code is far from being reliable though (at
the momment).

The flaw is a out-of-bounds indexing. We can fully control the 16 bit
value used as index within the function table.

srv2.sys (Vista)

text:000156B3 loc_156B3: ; CODE XREF: Smb2ValidateProviderCallback(x)+4D5j
.text:000156B3                                         ;
.text:000156B3  movzx   eax, word ptr [esi+0Ch];
.text:000156B7  mov     eax, _ValidateRoutines[eax*4]; 		
			BUG - out-of-bounds dereference.
.text:000156BE  test    eax, eax
.text:000156C0  jnz     short loc_156C9
.text:000156C2  mov     eax, 0C0000002h
.text:000156C7  jmp     short loc_156CC
.text:000156C9 ; —————————————————————————
.text:000156C9 loc_156C9:  ; CODE XREF:
.text:000156C9  push    ebx
.text:000156CA  call    eax ; Smb2ValidateNegotiate(x) ;
Smb2ValidateNegotiate(x) - KABOOOM!!


* The exploit provided by Lauren Gaffié ( the researcher who discovered
the flaw ) may or may not work since it is based on dereferencing a
non-paged memory page. If the original exploit didn't work, it would
probably deferenced a zeroed memory. You can try ProcessIDHigh values >
0x13 since any of these should trigger the flaw.

Affected versions: Windows Vista - Windows 7 - Windows server 2008.


More technical details (english)

Detalles técnicos (castellano)