Windows Remote Assistance Exploit Lets Hackers Steal Sensitive Files - Mr. R3x

Windows Remote Assistance Exploit Lets Hackers Steal Sensitive Files

You have always been warned not to share remote access to your computer with untrusted people for any reason—it's a basic cybersecurity advice, and common sense, right?

But what if, I say you should not even trust anyone who invites or offer you full remote access to their computers.

A critical vulnerability has been discovered in Microsoft's Windows Remote Assistance (Quick Assist) feature that affects all versions of Windows to date, including Windows 10, 8.1, RT 8.1, and 7, and allows remote attackers to steal sensitive files on the targeted machine.

Windows Remote Assistance is a built-in tool that allows someone you trust to take over your PC (or you to take remote control of others) so they can help you fix a problem from anywhere around the world.

The feature relies on the Remote Desktop Protocol (RDP) to establish a secure connection with the person in need.

However, Nabeel Ahmed of Trend Micro Zero Day Initiative discovered and reported an information disclosure vulnerability (CVE-2018-0878) in Windows Remote Assistance that could allow attackers to obtain information to further compromise the victim's system.

The vulnerability, which has been fixed by the company in this month's patch Tuesday, resides in the way Windows Remote Assistance processes XML External Entities (XXE).

The vulnerability affects Microsoft Windows Server 2016, Windows Server 2012 and R2, Windows Server 2008 SP2 and R2 SP1, Windows 10 (both 32- and 64-bit), Windows 8.1 (both 32- and 64-bit) and RT 8.1, and Windows 7 (both 32- and 64-bit).

Exploiting Windows Remote Assistance to Steal Files

Since a security patch for this vulnerability is now available, the researcher has finally released technical details and proof-of-concept exploit code for the flaw to the public.

In order to exploit this flaw, which resides in MSXML3 parser, the hacker needs to use "Out-of-Band Data Retrieval" attack technique by offering the victim access to his/her computer via Windows Remote Assistance.

While setting up Windows Remote Assistance, the feature gives you two options—Invite someone to help you and Respond to someone who needs help.

Selecting the first option helps users generate an invitation file, i.e. 'invitation.msrcincident,' which contains XML data with a lot of parameters and values required for authentication.

Since the parser does not properly validate the content, the attacker can simply send a specially crafted Remote Assistance invitation file containing a malicious payload to the victim, tricking the targeted computer to submit the content of specific files from known locations to a remote server controlled by the attackers.

"The stolen information could be submitted as part of the URL in HTTP request(s) to the attacker. In all cases, an attacker would have no way to force a user to view the attacker-controlled content. Instead, an attacker would have to convince a user to take action," Microsoft explains. 

"This XXE vulnerability can be genuinely used in mass scale phishing attacks targeting individuals believing they are truly helping another individual with an IT problem. Totally unaware that the .msrcincident invitation file could potentially result in loss of sensitive information," Ahmed warns.

Among patching other critical vulnerabilities fixed this month, Windows users are highly recommended to install the latest update for Windows Remote Assistance as soon as possible.

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[Guide] How to Protect Your Devices Against Meltdown and Spectre Attacks

[Guide] How to Protect Your Devices Against Meltdown and Spectre Attacks

Recently uncovered two huge processor vulnerabilities called Meltdown and Spectre have taken the whole world by storm, while vendors are rushing out to patch the vulnerabilities in its products.

The issues apply to all modern processors and affect nearly all operating systems (Windows, Linux, Android, iOS, macOS, FreeBSD, and more), smartphones and other computing devices made in the past 20 years.

What are Spectre and Meltdown?

We have explained both, Meltdown (CVE-2017-5754) and Spectre (CVE-2017-5753, CVE-2017-5715), exploitation techniques in our previous article.

In short, Spectre and Meltdown are the names of security vulnerabilities found in many processors from Intel, ARM and AMD that could allow attackers to steal your passwords, encryption keys and other private information.

Both attacks abuse 'speculative execution' to access privileged memory—including those allocated for the kernel—from a low privileged user process like a malicious app running on a device, allowing attackers to steal passwords, login keys, and other valuable information.

Protect Against Meltdown and Spectre CPU Flaws

Some, including US-CERT, have suggested the only true patch for these issues is for chips to be replaced, but this solution seems to be impractical for the general user and most companies.

Vendors have made significant progress in rolling out fixes and firmware updates. While the Meltdown flaw has already been patched by most companies like Microsoft, Apple and Google, Spectre is not easy to patch and will haunt people for quite some time.

Here's the list of available patches from major tech manufacturers:

Windows OS (7/8/10) and Microsoft Edge/IE

Microsoft has already released an out-of-band security update (KB4056892) for Windows 10 to address the Meltdown issue and will be releasing patches for Windows 7 and Windows 8 on January 9th.

But if you are running a third-party antivirus software then it is possible your system won’t install patches automatically. So, if you are having trouble installing the automatic security update, turn off your antivirus and use Windows Defender or Microsoft Security Essentials.

"The compatibility issue is caused when antivirus applications make unsupported calls into Windows kernel memory," Microsoft noted in a blog post. "These calls may cause stop errors (also known as blue screen errors) that make the device unable to boot."

Apple macOS, iOS, tvOS, and Safari Browser

Apple noted in its advisory, "All Mac systems and iOS devices are affected, but there are no known exploits impacting customers at this time."

To help defend against the Meltdown attacks, Apple has already released mitigations in iOS 11.2, macOS 10.13.2, and tvOS 11.2, has planned to release mitigations in Safari to help defend against Spectre in the coming days.

Android OS

Android users running the most recent version of the mobile operating system released on January 5 as part of the Android January security patch update are protected, according to Google.

So, if you own a Google-branded phone, like Nexus or Pixel, your phone will either automatically download the update, or you'll simply need to install it. However, other Android users have to wait for their device manufacturers to release a compatible security update.

The tech giant also noted that it's unaware of any successful exploitation of either Meltdown or Spectre on ARM-based Android devices.

Firefox Web Browser

Mozilla has released Firefox version 57.0.4 which includes mitigations for both Meltdown and Spectre timing attacks. So users are advised to update their installations as soon as possible.

"Since this new class of attacks involves measuring precise time intervals, as a partial, short-term mitigation we are disabling or reducing the precision of several time sources in Firefox," Mozilla software engineer Luke Wagner wrote in a blog post.

Google Chrome Web Browser

Google has scheduled the patches for Meltdown and Spectre exploits on January 23 with the release of Chrome 64, which will include mitigations to protect your desktop and smartphone from web-based attacks.

In the meantime, users can enable an experimental feature called "Site Isolation" that can offer some protection against the web-based exploits but might also cause performance problems.

"Site Isolation makes it harder for untrusted websites to access or steal information from your accounts on other websites. Websites typically cannot access each other's data inside the browser, thanks to code that enforces the Same Origin Policy." Google says.

Here's how to turn on Site Isolation:

• Copy chrome://flags/#enable-site-per-process and paste it into the URL field at the top of your Chrome web browser, and then hit the Enter key.
• Look for Strict Site Isolation, then click the box labelled Enable.
• Once done, hit Relaunch Now to relaunch your Chrome browser.

Linux Distributions

The Linux kernel developers have also released patches for the Linux kernel with releases including versions 4.14.11, 4.9.74, 4.4.109, 3.16.52, 3.18.91 and 3.2.97, which can be downloaded from Kernel.org.

VMware and Citrix

A global leader in cloud computing and virtualisation, VMware, has also released a list of its products affected by the two attacks and security updates for its ESXi, Workstation and Fusion products to patch against Meltdown attacks.

On the other hand, another popular cloud computing and virtualisation vendor Citrix did not release any security patches to address the issue. Instead, the company guided its customers and recommended them to check for any update on relevant third-party software.

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Meltdown and Spectre CPU Flaws Affect Intel, ARM, AMD Processors

Meltdown and Spectre CPU Flaws Affect Intel, ARM, AMD Processors 

Unlike the initial reports suggested about Intel chips being vulnerable to some severe ‘memory leaking’ flaws, full technical details about the vulnerabilities have now been emerged, which revealed that almost every modern processor since 1995 is vulnerable to the issues.

Disclosed today by Google Project Zero, the vulnerabilities potentially impact all major CPUs, including those from AMD, ARM, and Intel—threatening almost all PCs, laptops, tablets, and smartphones, regardless of manufacturer or operating system.

These hardware vulnerabilities have been categorized into two attacks, named Meltdown (CVE-2017-5754) and Spectre (CVE-2017-5753 and CVE-2017-5715), which could allow attackers to steal sensitive data which is currently processed on the computer.

Both attacks take advantage of a feature in chips known as "speculative execution," a technique used by most modern CPUs to optimize performance.

"In order to improve performance, many CPUs may choose to speculatively execute instructions based on assumptions that are considered likely to be true. During speculative execution, the processor is verifying these assumptions; if they are valid, then the execution continues. If they are invalid, then the execution is unwound, and the correct execution path can be started based on the actual conditions," Project Zero says.

Therefore, it is possible for such speculative execution to have "side effects which are not restored when the CPU state is unwound and can lead to information disclosure," which can be accessed using side-channel attacks.

Meltdown Attack

The first issue, Meltdown (paper), allows attackers to read not only kernel memory but also the entire physical memory of the target machines, and therefore all secrets of other programs and the operating system.

“Meltdown is a related microarchitectural attack which exploits out-of-order execution in order to leak the target’s physical memory.”

Meltdown uses speculative execution to break the isolation between user applications and the operating system, allowing any application to access all system memory, including memory allocated for the kernel.

“Meltdown exploits a privilege escalation vulnerability specific to Intel processors, due to which speculatively executed instructions can bypass memory protection.”

Nearly all desktop, laptop, and cloud computers affected by Meltdown.

Spectre Attack

The second problem, Spectre (paper), is not easy to patch and will haunt people for quite some time since this issue requires changes to processor architecture in order to fully mitigate.

Spectre attack breaks the isolation between different applications, allowing the attacker-controlled program to trick error-free programs into leaking their secrets by forcing them into accessing arbitrary portions of its memory, which can then be read through a side channel.

Spectre attacks can be used to leak information from the kernel to user programs, as well as from virtualization hypervisors to guest systems.

“In addition to violating process isolation boundaries using native code, Spectre attacks can also be used to violate browser sandboxing, by mounting them via portable JavaScript code. We wrote a JavaScript program that successfully reads data from the address space of the browser process running it.” the paper explains.

“KAISER patch, which has been widely applied as a mitigation to the Meltdown attack, does not protect against Spectre.”

According to researchers, this vulnerability impacts almost every system, including desktops, laptops, cloud servers, as well as smartphones—powered by Intel, AMD, and ARM chips.

What You Should Do: Mitigations And Patches

Many vendors have security patches available for one or both of these attacks.

• Windows — Microsoft has issued an out-of-band patch update for Windows 10, while other versions of Windows will be patched on the traditional Patch Tuesday on January 9, 2018
• MacOS — Apple had already fixed most of these security holes in macOS High Sierra 10.13.2 last month, but MacOS 10.13.3 will enhance or complete these mitigations.
• Linux — Linux kernel developers have also released patches by implementing kernel page-table isolation (KPTI) to move the kernel into an entirely separate address space.
• Android — Google has released security patches for Pixel/Nexus users as part of the Android January security patch update.  Other users have to wait for their device manufacturers to release a compatible security update.

Mitigations for Chrome Users

Since this exploit can be executed through the website, Chrome users can turn on Site Isolation feature on their devices to mitigate these flaws.

Here's how to turn Site Isolation on Windows, Mac, Linux, Chrome OS or Android:

• Copy chrome://flags/#enable-site-per-process and paste it into the URL field at the top of your Chrome web browser, and then hit the Enter key.
• Look for Strict Site Isolation, then click the box labeled Enable.
• Once done, hit Relaunch Now to relaunch your Chrome browser.

There is no single fix for both the attacks since each requires protection independently.

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Microsoft Releases Patches for 16 Critical Flaws, Including a Zero-Day

Microsoft Releases Patches for 16 Critical Flaws, Including a Zero-Day

If you think that only CPU updates that address this year's major security flaws—Meltdown and Spectre—are the only ones you are advised to grab immediately, there are a handful of major security flaws that you should pay attention to.

Microsoft has issued its first Patch Tuesday for 2018 to address 56 CVE-listed flaws, including a zero-day vulnerability in MS Office related that had been actively exploited by several threat groups in the wild.

Sixteen of the security updates are listed as critical, 38 are rated important, one is rated moderate, and one is rated as low in severity. The updates address security flaws in Windows, Office, Internet Explorer, Edge, ChakraCore, ASP.NET, and the .NET Framework.

The zero-day vulnerability (CVE-2018-0802), described by Microsoft as a memory corruption flaw in Office, is already being targeted in the wild by several threat actor groups in the past few months.

The vulnerability, discovered by several researchers from Chinese companies Tencent and Qihoo 360, ACROS Security's 0Patch Team, and Check Point Software Technologies, can be exploited for remote code execution by tricking a targeted user into opening a specially crafted malicious Word file in MS Office or WordPad.

According to the company, this security flaw is related to CVE-2017-11882—a 17-year-old vulnerability in the Equation Editor functionality (EQNEDT32.EXE), which Microsoft addressed in November.

When researchers at 0Patch were analysing CVE-2017-11882, they discovered a new, related vulnerability (CVE-2018-0802). More details of CVE-2018-0802 can be found in a blog post published by Check Point.

Besides CVE-2018-0802, the company has addressed nine more remote code execution and memory disclosure vulnerabilities in MS Office.

A spoofing vulnerability (CVE-2018-0819) in Microsoft Outlook for MAC, which has been listed as publicly disclosed (Mailsploit attack), has also addressed by the company. The vulnerability does not allow some versions Outlook for Mac to handle the encoding and display of email addresses properly, causing antivirus or anti-spam scanning not to work as intended.

Microsoft also addressed a certificate validation bypass vulnerability (CVE-2018-0786) in .NET Framework (and .NET Core) that could allow malware authors to show their invalid certificates as valid.

"An attacker could present a certificate that is marked invalid for a specific use, but the component uses it for that purpose," describes Microsoft. "This action disregards the Enhanced Key Usage taggings."

The company has also patched a total of 15 vulnerabilities in the scripting engine used by Microsoft Edge and Internet Explorer.

All these flaws could be exploited for remote code execution by tricking a targeted user into opening a specially-crafted webpage that triggers a memory corruption error, though none of these has been exploited in the wild yet.

Meanwhile, Adobe has patched a single, out of bounds read flaw (CVE-2018-4871) this month that could allow for information disclosure, though no active exploits have been seen in the wild.

Users are strongly advised to apply security patches as soon as possible to keep hackers and cybercriminals away from taking control of their computers.

For installing security updates, simply head on to Settings → Update & security → Windows Update → Check for updates, or you can install the updates manually.

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