Re: has a new story showing how to use this backdoor, and various Twitter news sites are also covering this. 🙂

BTW, the blog site for Dmytro has been down for a few days. A few months ago, it was down for about a week. Hopefully it’ll come back again.



Cr4sh’s DmaHvBackdoor.c: Hyper-V backdoor for UEFI

Cr4sh is having fun with Windows Device Guard:

DmaHvBackdoor.c comments:

Part of UEFI DXE driver code that injects Hyper-V VM exit handler backdoor into the Device Guard enabled Windows 10 Enterprise. Execution starts from new_ExitBootServices() — a hook handler for EFI_BOOT_SERVICES.ExitBootServices() which being called by winload!OslFwpKernelSetupPhase1(). After DXE phase exit winload.efi transfers exeution to previously loaded Hyper-V kernel (hvix64.sys) by calling winload!HvlpTransferToHypervisor(). To transfer execution to Hyper-V winload.efi uses a special stub winload!HvlpLowMemoryStub() copied to reserved memory page at constant address 0x2000. During runtime phase this memory page is visible to hypervisor core at the same virtual and physical address and has executable permissions which makes it a perfect place to store our Hyper-V backdoor code. VMExitHandler() is a hook handler for VM exit function of hypervisor core, it might be used for interaction between hypervisor backdoor and guest virtual machines.

WordPress chokes on Github gist-based URLs, so click on initial Tweet above for URL. Or look for entry that matches date:

Dmytro’s Rogue PCI-E device


scan_thinkpwn: searches for ThinkPwn vulnerability

THINKPWN SCANNER: This program is used to scan UEFI drivers extracted from firmware image for ThinkPwn vulnerability in vendor/model agnostic way.
@d_olex (aka Cr4sh) — initial Vivisect based version of the program;

@trufae (aka pankake) — radare2 based version (this one);

Read the source code for more user docs, including a detailed source comment about how the code works.

More info:

Intel NUC’s Vulnerable to SMM Exploit

A new Intel Security Center advisory:

Intel® Branded NUC’s Vulnerable to SMM Exploit
Intel ID:      INTEL-SA-00057
Product family:      Intel® NUC Kits
Impact of vulnerability:      Elevation of Privilege
Severity rating:      Important
Original release:      Oct 03, 2016
Last revised:      Nov 15, 2016

Intel is releasing updated BIOS firmware for a privilege escalation issue. This issue affects Intel® NUC Kits listed in the affected products section below. The issue identified is a method that enables malicious code to gain access to System Management Mode (SMM). A malicious attacker with local administrative access can leverage the vulnerable BIOS to gain access to System Management Mode (SMM) and take full control of the platform. Intel products that are listed below should apply the update. Intel highly recommends updating the BIOS of all Intel® NUC’s to the recommended BIOS or later listed in the table of affected products. Intel would like to thank Security Researcher Dmytro Oleksiuk for discovering and reporting this issue.

Dmytro takes on the Intel NUC

Dmytro Oleksiuk has a new blog post with UEFI security issues with an Intel NUC using AMI Aptio UEFI BIOS.

(Sad to see that Intel appears to not appear to run CHIPSEC as part of release management QA their own NUCs.)

Exploiting AMI Aptio firmware on example of Intel NUC
[…] Today I’m sharing with you the story of my next x86 machine hacking — we’re going to talk about UEFI vulnerabilities, exploit mitigation features of System Management Mode and new exploit called Aptiocalypsis. Also, this time I did responsible disclosure to Intel and AMI, so, at the moment of this publication you already can patch some of vulnerable products.

Lots of interesting things happened since release of ThinkPwn exploit. Firstly I supposed that vulnerable code was written by Lenovo or its Independent BIOS Vendor (IBV), but later it turned out that they’ve taken this totally mad driver from Intel reference code. This exact code is not available in public, but open source firmware of some Intel boards has it too. For example, SmmRuntimeManagementCallback() function from Intel Quark BSP it’s exactly the same vulnerable code that I’ve found in firmware of my T450s. It’s also interesting that vulnerable code is quite old (it comes from EFI 1.x era) but nevertheless, it was never present in EDK2 source from public repository — its version of QuarkSocPkg was heavily modified in comparison with vulnerable one. The horrible and vulnerable by design piece of code was removed by Intel somewhere in the middle of 2014, but it seems that there were no security advisories regarding this issue. Due to this IBVs had no chance to fix this vulnerability in their relatively old code base and the bug appeared in modern computers from Lenovo, Intel, GIGABYTE, Dell, HP, Fujitsu and other OEM’s (oops!).

Well, I guess at this point it’s much or less clear that currently there’s nothing to do with ThinkPad anymore, it was pwned with 0day, it has too awkward code base that follows ancient version of EFI specification and 8 series chipset that is not the freshest stuff you can get. As my next target for firmware security adventures I’ve decided to take some Skylake based machine of well-known vendor who might have a decent firmware that would be interesting to break. Because I like all kinds of small x86 compatible computers, I’ve put my eye on the latest generation of Intel NUC. It also looks interesting because platform vendor knows his hardware better than anyone else, so, from firmware security perspective, Intel NUC is definitely not the worst choice.[…]


PeiBackdoor: new UEFI payload/backdoor tool

Dmytro Oleksiuk (aka Cr4sh) has created a new UEFI security researcher tool: PeiBackdoor, which hooks into the init code of UEFI. (PEI is the Pre-uEfi-Init phase, before all the UEFI protocols are in place, the init code of UEFI.) It uses Capstone, and requires Windows.

PEI stage backdoor for UEFI compatible firmware

This project implements early stage firmware backdoor for UEFI based firmware. It allows to execute arbitrary code written in C during Pre EFI Init (PEI) phase of Platform Initialization (PI). This backdoor might be useful for low level manipulations with the target platform configuration when the most of the platform configuration registers are not locked yet. […]

PEI backdoor project includes:

* – Python program that allows to infect raw flash images or individual UEFI PEI drivers with the backdoor code.
* PeiBackdoor_IA32.efi, PeiBackdoor_IA32.pdb – 32-bit PEI backdoor binary compiled with ACTIVE_PLATFORM = IA32.
* PeiBackdoor_X64.efi, PeiBackdoor_X64.pdb – 64-bit PEI backdoor binary compiled with ACTIVE_PLATFORM = X64.
* PeiBackdoor.inf – PEI backdoor project configuration for EDK2 build environment.
* config.h – PEI backdoor build options.
* payload.c – Put your own PEI stage code into this source file and call it from Payload() function.
* src/ – Rest of the PEI backdoor code. is using Capstone engine and pefile Python libraries, you need to install them with pip install capstone pefile command.

ThinkPwn updated


New tool:
Extract SW SMI handlers information from SMRAM dump of Skylake based AMI Aptio V firmware.

Hmm, WordPress renders Github gist pages to be unviewable. Remove the SPACE character after the TLD in the below URL to make it work. Or click on the links in the Twitter links.  /Cr4sh/db43cc6687e737d982d3d1c56472c6b9

exploiting Lenovo firmware, part 2D

A bit more on this:

Lenovo has updated their support document. The initial version had no technical details. The update now has a huge list of models which are affected or not. The researcher also mentions that an update from the vendor is expected next month. I’m still waiting to see the IBV’s and other OEMs responses to this.


exploiting Lenovo firmware, part 2C

A bit more on this:

exploiting Lenovo firmware, part 2B

more on this:

Lenovo has a response:

System Management Mode (SMM) BIOS Vulnerability
Lenovo Security Advisory:  LEN-8324
Potential Impact:  Execution of code in SMM by an attacker with local administrative access
Severity:  High
Scope of Impact: Industry-wide

The researcher also has a few responses:


exploiting Lenovo firmware, part 2A

A few bits of news to add to this:

These days, it is nice to know that a firmware bug is probably an accidental defect, rather than some backdoor.  🙂

In 2015, UEFI Forum used to do Security Advisories, with 2 PDFs each containing more than a dozen potential exploits. I wonder how many of those are in today’s vendors codebases? No more advisories from UEFI Forum since 2015, so who knows what other cut-and-paste OEM/IBV bugs are being propogated? I wish UEFI Forum would issue more Security Advisories, multiple bugfixes on the EDK2-devel project appear to merit this kind of attention.

exploiting Lenovo firmware, part 2

Cr4sh has written the second article in his series on Lenovo firmware security research:

Exploring and exploiting Lenovo firmware secrets
Hi, everyone! In this article I will continue to publish my research of Lenovo ThinkPad’s firmware. Previously I shown how to discover and exploit SMM callout vulnerabilities on example of SystemSmmAhciAspiLegacyRt UEFI driver 1day vulnerability. Also, I introduced a small toolkit called fwexpl that provides API for comfortable development of firmware exploits for Windows platform. My previous Lenovo exploit was able to execute custom code in SMM, such conditions allow relatively easy bypass of BIOS_CNTL security mechanism which protect firmware code stored inside SPI flash chip on motherboard from unauthorized modifications by operating system (BIOS_CNTL bypass also was discussed in my another article “Breaking UEFI security with software DMA attacks”). In addition to BIOS_CNTL, modern Lenovo computers also use SPI Protected Ranges (aka PRx) flash write protection, so, in this article I will present my generic exploitation technique that allows to bypass PRx and turn arbitrary SMM code execution vulnerability into the flash write protection bypass exploit. This technique also can be applied to UEFI compatible computers of other manufacturers — they all use similar design of specific firmware features that responsible for platform security. In second part of the article I will present a new 0day vulnerability in Lenovo firmware that allows arbitrary SMM code execution on a wide range of Lenovo models and firmware versions including the most recent ones. Exploitation of this vulnerability may lead to the flash write protection bypass, disabling of UEFI Secure Boot, Virtual Secure Mode and Credential Guard bypass in Windows 10 Enterprise and other evil things. […]

Cr4sh on SMM exploits in Lenovo firmware!

Dmytro Oleksiuk aka Cr4sh has a new blog post on SMM exploits on Lenovo firmware! Very well written and detailed, with source code!

Exploiting SMM callout vulnerabilities in Lenovo firmware
Hi, everyone. In this article I’ll continue to publish my research in PC firmware security field. In previous article, “Breaking UEFI security with software DMA attacks”, I’ve shown how to exploit UEFI boot script table vulnerability and get access to the SMRAM using software DMA attack under Linux. This time we will talk about discovering and exploitation of SMI dispatch vulnerabilities in UEFI System Management Mode drivers. For anyone who’s not familiar with architecture of SMM phase firmware code on UEFI based platforms I’ll strongly recommend to read my other article “Building reliable SMM backdoor for UEFI based platforms”, especially the part about communicating with SMM code using software SMI.

SMM vulnerabilities that I will talk about in this article aren’t new. Around one year ago LegbaCore and Intel Security published two works: “How Many Million BIOSes Would you Like to Infect?” and “A New Class of Vulnerabilities in SMI Handlers” correspondingly, they rediscovered some security issues in SMI handlers code that was actually a known problem among PC firmware developers (for example, same attacks was described in Loïc Duflot work “System Management Mode Design and Security Issues” presented six years ago). Nevertheless, researchers were able to find and report a lot of firmware vulnerabilities of this class in products like Lenovo, Dell, HP laptops and many others (CERT VU#631788). To play with these vulnerabilities I got ThinkPad T450s laptop. According to original security advisory by Lenovo (apparently, it has a lack of technical details) — some unspecified SMM callout vulnerabilities were patched in the latest version of it’s firmware and everything that we need to do is just find out and exploit one of these vulns. […]


Using UEFI_boot_script_expl on Lenovos

Dmytro “Cr4sh” Oleksiuk has a conversation on Twitter about using using his CHIPSEC-based exploit module against Lenovo models, noting some firmware vulnerabilities in Lenovo x220/x230 laptops.

Here are 5 tweets, let’s see how the non-deterministic rendering software will show them:

It is nice to hear “The most recent ones looks not vulnerable.” Maybe the Lenovo QA team is improving? 🙂 Looking forward to more research on this, more than just a few Tweets, his research is usually very verbose! Also, he has updated the readme on his update script today:

UEFI SMM vulnerability research: SmmBackdoor

Dmytro ‘Cr4sh’ Oleksiuk has been looking into Intel Systems Management Mode (SMM) on UEFI systems. Yesterday he posted a blog with some information on this research, along with some source code. Check out the blog post, it’s a very long document with lots of figures, very good reading.

More Information: