Vulnerability title: Privilege Escalation in ESET Windows Products
CVE: CVE-2014-4973
Vendor: ESET
Product: ESET Windows Products
Affected version: v5.0 - 7.0 (Firewall Module Build 1183 (20140214) and
earlier)
Fixed version: v6 - v7 (Firewall Module Build 1212 (20140609))
Reported by: Kyriakos Economou

Details:

Versions 5.0 – 7.0 of ESET Smart Security and ESET Endpoint Security products for Windows XP OS allow a low privileged user to execute code as SYSTEM by exploiting a vulnerability in the ESET Personal Firewall NDIS filter (EpFwNdis.sys) kernel mode driver also mentioned as Personal Firewall module: Build 1183 (20140214) and prior. This is a ‘trusted value vulnerability’ that can be triggered through a specific IOCTL with a specifically crafted buffer, to force the driver to validate an improper IOCTL.

EpFwNdis.sys registers NDIS!ndisDeviceControlIrpHandler as the dispatch function for the IRP_MJ_DEVICE_CONTROL IRP function code.

Through IOCTL 0x830020CC we arrive at EpFwNdis+0x43f6 where the trusted value vulnerability is triggered:

*ba2ac41c 3b4d08 cmp ecx,dword ptr [ebp+8] <--- we can control the value at [ebp+8] from userland

Matching ECX value means that we can keep controlling the execution and force it to validate some other parameters that we send through the IOCTL input buffer.
Getting the proper value can be achieved either by triggering a kernel memory leak vulnerability present in the same driver module (version agnostic), or by getting its base address and send the correct offset through the IOCTL. The magic value is stored inside the driver image itself so by knowing the base address we can calculate the RVA for it.

Finally we will arrive here:

wanarp!WanNdisReceiveComplete <--- function name in wanarp.sys
call dword ptr [wanarp!g_pfnIpRcvComplete (ba29dfb4)] <---- 0x00000000

As NULL pages can be allocated in Windows XP, we can put to 0×00000000 a trampoline to our payload and execute code with kernel privileges.

Impact:

This vulnerability could allow a malicious attacker to gain Administrator privileges on a system from a user account.

Exploit:

The proof of concept exploit is available. 

Further details at:
https://www.portcullis-security.com/security-research-and-downloads/security-advisories/cve-2014-4973/


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