CVE: CVE-2015-1438
Vendor: Panda Security
Product: Multiple Products
Affected version: 1.0.0.13 (PSKMAD.sys driver version)
Fixed version: 15.1.0 (Products Version)
Reported by: Kyriakos Economou (@kyREcon)
Advisory
Panda Kernel Memory Access Driver doesn’t validate the size of data to be copied to both an allocated kernel paged pool buffer and to an allocated non-paged pool buffer. Furthermore, the attacker has control over the start-to-copy index regarding the non-paged pool buffer which allows an attacker to corrupt a kernel object with more precision, and control the EIP via a hijacked function pointer.
Technical Details
b5ae8cc5 8b7508 mov esi,dword ptr [ebp+8]
b5ae8cc8 0fb7460c movzx eax,word ptr [esi+0Ch]
b5ae8ccc 6685c0 test ax,ax
b5ae8ccf 7674 jbe PSKMAD_b5ae4000+0x4d45 (b5ae8d45)
b5ae8cd1 668b4e0e mov cx,word ptr [esi+0Eh]
b5ae8cd5 668945f4 mov word ptr [ebp-0Ch],ax
b5ae8cd9 0fb7c0 movzx eax,ax
b5ae8cdc 6850534d45 push 454D5350h <-- 'PSME' pool tag
b5ae8ce1 50 push eax
b5ae8ce2 6a01 push 1
b5ae8ce4 66894df6 mov word ptr [ebp-0Ah],cx
b5ae8ce8 ff159ca6aeb5 call dword ptr [PSKMAD_b5ae4000+0x669c]={nt!ExAllocatePoolWithTag}
b5ae8cee 8945f8 mov dword ptr [ebp-8],eax
b5ae8cf1 85c0 test eax,eax
b5ae8cf3 7550 jne PSKMAD_b5ae4000+0x4d45 (b5ae8d45)
...
b5ae8d45 8d4608 lea eax,[esi+8]
b5ae8d48 50 push eax b5ae8d49 8d45f4 lea eax,[ebp-0Ch]
b5ae8d4c 50 push eax
b5ae8d4d ff36 push dword ptr [esi]
b5ae8d4f ff1514a7aeb5 call dword ptr [PSKMAD_b5ae4000+0x6714]={nt!ZwQuerySymbolicLinkObject}
b5ae8d55 894604 mov dword ptr [esi+4],eax
b5ae8d58 85c0 test eax,eax
b5ae8d5a 7d09 jge PSKMAD_b5ae4000+0x4d65 (b5ae8d65)
...
b5ae8d65 0fb745f4 movzx eax,word ptr [ebp-0Ch]
b5ae8d69 50 push eax
b5ae8d6a 8b4610 mov eax,dword ptr [esi+10h]
b5ae8d6d ff75f8 push dword ptr [ebp-8]
b5ae8d70 03c6 add eax,esi
b5ae8d72 50 push eax
b5ae8d73 e864120000 call PSKMAD_b5ae4000+0x5fdc (b5ae9fdc)
Impact
An exploit can potentially use either of the two aforementioned bugs to trigger a heap overflow condition that would allow to execute code with Kernel privileges. However, the second heap overflow bug is much more interesting because it allows a precise control of the index to start copying the symbolic link target returned by a call to the nt!ZwQuerySymbolicLinkObject kernel function.
This allows an attacker to corrupt with precision a kernel object that we control that has been previously put there by performing heap spraying at the non-paged kernel pool. The attacker can use part of the symbolic link target as a pointer to a predictable memory range in userland where a trampoline to the payload is stored.