CVE-2014-7136 - Privilege Escalation In K7 Computing Multiple Products [K7FWFilt.sys]

[Portcullis Advisories <advisories () portcullis-security com>]

Vulnerability title: Privilege Escalation In K7 Computing Multiple Products [K7FWFilt.sys]
CVE: CVE-2014-7136
Vendor: K7 Computing
Product: Multiple Products [K7FWFilt.sys]
Affected version: Earlier and including 11.0.1.5
Fixed version: 14.0.1.16
Reported by: Kyriakos Economou
Details:

Latest, and possibly earlier versions of K7FWFilt.sys kernel mode driver, also named as the 'K7Firewall Packet Driver', 
suffers from a heap overflow condition that can be exploited locally by an attacker in order to execute code with 
kernel privileges. Successful exploitation of this bug results in vertical privilege escalation.

Technical Details:

The function handling IOCTL 0x830020C4 does not validate the size of the output buffer parameter passed in the 
DeviceIoControl API, which leads to a heap overflow on buffer data initialization. In particular, the function assumes 
that the output buffer has a size of 0x22C4 bytes. By declaring a smaller buffer we are able to overwrite other data 
and kernel objects that might follow and potentially control the execution flow via a corrupted kernel object.

ba31cb06 8b7d14 mov edi,dword ptr [ebp+14h] <--- EDI == allocated buffer
ba31cb09 ff7514 push dword ptr [ebp+14h]
ba31cb0c b9b1080000 mov ecx,8B1h <--- assume buffer size 0x8b1 * 4
ba31cb11 33c0 xor eax,eax <--- zero out EAX
ba31cb13 f3ab rep stos dword ptr es:[edi] <--- Heap Overflow

Further details at:

https://www.portcullis-security.com/security-research-and-downloads/security-advisories/cve-2014-7136/

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