Sep 21 2017

Microsoft Kills Potential Remote Code Execution Vulnerability in Office (CVE-2017-8630)

Recently the McAfee IPS Research Team informed Microsoft about a potential remote code execution vulnerability in Office 2016 that McAfee discovered in March. Microsoft released a patch for this vulnerability this week with CVE-2017-8630. In this post, we will briefly discuss the vulnerability and its exploitability.

The Problem

While auditing PowerPoint, we came across an interesting application crash. The stack trace looked like this:

When we disassembled the crash point we noticed something interesting.

We saw the access violation occurred at address 0x6631508d. And at address 0x66315090 we noticed a call instruction. From these instructions it appeared the code was trying to call a virtual function from the vtable of an object. To make sure, we quickly enabled a page heap for PowerPoint and tried to reproduce the issue.

The page heap made it clear that the issue was a dangling pointer, a “use after free” case. The preceding screenshot shows that the object being accessed was already free. Although we identified the issue while examining PowerPoint, digging further reveals the issue lies in some Office 2016 shared functionality. The problem affects not only PowerPoint, but other applications as well. On September 12 Microsoft published a patch confirming that Office 2016 (32-bit and 64-bit editions) is affected by this problem.

Triggering the Condition

This use-after-free condition is not easy to trigger. When we open the proof-of-concept file in PowerPoint, several pop-up windows appear. We need to choose a specific set of options to exploit the vulnerability. The time gap between choosing the options also matters.

After several trials, we noticed the object is freed when we suppress the first pop-up and select OK. The object reuse happens when selecting the Repair option in the second window. This sequence is very helpful when we move to exploit this vulnerability.


Our exploitation strategy was the same as for any other use-after-free vulnerability. However, due to the absence of an interactive engine in Office, preparing the memory layout for the exploitation was challenging. In this case we used an ActiveX object to spray office memory and set up the desired memory layout. Two excellent papers explain how to prepare a desired memory layout to exploit Office.

These papers discuss the technique mostly with Word. However, we ported the same technique to PowerPoint. The following diagram shows the exploitation strategy at a glance:

Preparing the Memory Layout

Our first step in preparing the memory layout is to make sure that controlled data is present at known addresses, such as 0x0a0a0a0a and 0x0c0c0c0c.

The preceding screen shows how to use heap spray to place our controlled data at a predictable address. Address 0x0a0a0a0a has the data 0xdebadeba and some no-operation slides. To be more specific, for exploitation we need an address that we control at 0x0a0a0a0a + 0x8.

The next challenge is to create a fake object in a PowerPoint process of the same size as our object. To make sure we can claim the same freed heap block for our fake object, we must spray the memory several times so that the heap manager forcefully places the fake object where the real object was situated. We must spray the memory with same size multiple times using the pattern 0x0a0a0a0a. Thus when the virtual function is called using the object under our control, it will dereference the value from our heap spray (as we performed in last section) at the address 0x0a0a0a0a + 0x8.

So far, we have not done anything to the PowerPoint file that triggers the use-after-free vulnerability. We have just set the stage on which we will perform the exploitation. Once we have everything in place, we carefully port the heap-spraying code to the open XML file, which triggers the use after free.

The preceding screen shows, once everything is in right place, the register ecx pointing to the fake object. When it is dereferenced, we get a pointer to the fake vtable in eax.

McAfee highly recommends that Office 2016 users apply the patch shipped by Microsoft this month. This vulnerability resides in some shared features and can be exploited through different Office 2016 products. McAfee Network Security Platform IPS can catch some exploits with the help of Signature 0x45217b00.

The author thanks Bing Sun for his help with this post.

The post Microsoft Kills Potential Remote Code Execution Vulnerability in Office (CVE-2017-8630) appeared first on McAfee Blogs.

Sep 21 2017

Joomla! Releases Security Update

Original release date: September 21, 2017

Joomla! has released version 3.8.0 of its Content Management System (CMS) software to address a vulnerability. A remote attacker could exploit this vulnerability to obtain access to sensitive information.

US-CERT encourages users and administrators to review the Joomla! Security Release and apply the necessary update.

This product is provided subject to this Notification and this Privacy & Use policy.

Sep 20 2017

Krebs on Security 2017-09-20 23:35:26

Bloomberg published a story this week citing three unnamed sources who told the publication that Equifax experienced a breach earlier this year which predated the intrusion that the big-three credit bureau announced on Sept. 7. To be clear, this earlier breach at Equifax is not a new finding and has been a matter of public record for months. Furthermore, it was first reported on this Web site in May 2017.

equihaxIn my initial Sept. 7 story about the Equifax breach affecting more than 140 million Americans, I noted that this was hardly the first time Equifax or another major credit bureau has experienced a breach impacting a significant number of Americans.

On May 17, KrebsOnSecurity reported that fraudsters exploited lax security at Equifax’s TALX payroll division, which provides online payroll, HR and tax services.

That story was about how Equifax’s TALX division let customers who use the firm’s payroll management services authenticate to the service with little more than a 4-digit personal identification number (PIN).

Identity thieves who specialize in perpetrating tax refund fraud figured out that they could reset the PINs of payroll managers at various companies just by answering some multiple-guess questions — known as “knowledge-based authentication” or KBA questions — such as previous addresses and dates that past home or car loans were granted.

On Tuesday, Sept. 18, Bloomberg ran a piece with reporting from no fewer than five journalists there who relied on information provided by three anonymous sources. Those sources reportedly spoke in broad terms about an earlier breach at Equifax, and told the publication that these two incidents were thought to have been perpetrated by the same group of hackers.

The Bloomberg story did not name TALX. Only post-publication did Bloomberg reporters update the piece to include a statement from Equifax saying the breach was unrelated to the hack announced on Sept. 7, and that it had to do with a security incident involving a payroll-related service during the 2016 tax year.

I have thus far seen zero evidence that these two incidents are related. Equifax has said the unauthorized access to customers’ employee tax records (we’ll call this “the March breach” from here on) happened between April 17, 2016 and March 29, 2017.

The criminals responsible for unauthorized activity in the March breach were participating in an insidious but common form of cybercrime known as tax refund fraud, which involves filing phony tax refund requests with the IRS and state tax authorities using the personal information from identity theft victims.

My original report on the March breach was based on public breach disclosures that Equifax was required by law to file with several state attorneys general.

Because the TALX incident exposed the tax and payroll records of its customers’ employees, the victim customers were in turn required to notify their employees as well. That story referenced public breach disclosures from five companies that used TALX, including defense contractor giant Northrop Grumman; staffing firm Allegis GroupSaint-Gobain Corp.; Erickson Living; and the University of Louisville.

When asked Tuesday about previous media coverage of the March breach, Equifax pointed National Public Radio (NPR) to coverage in KrebsonSecurity.

One more thing before I move on to the analysis. For more information on why KBA is a woefully ineffective method of stopping fraudsters, see this story from 2013 about how some of the biggest vendors of these KBA questions were all hacked by criminals running an identity theft service online.

Or, check out these stories about how tax refund fraudsters used weak KBA questions to steal personal data on hundreds of thousands of taxpayers directly from the Internal Revenue Service‘s own Web site. It’s probably worth mentioning that Equifax provided those KBA questions as well.


Over the past two weeks, KrebsOnSecurity has received an unusually large number of inquiries from reporters at major publications who were seeking background interviews so that they could get up to speed on Equifax’s spotty security history (sadly, Bloomberg was not among them).

These informational interviews — in which I agree to provide context and am asked to speak mainly on background — are not unusual; I sometimes field two or three of these requests a month, and very often more when time permits. And for the most part I am always happy to help fellow journalists make sure they get the facts straight before publishing them.

But I do find it slightly disturbing that there appear to be so many reporters on the tech and security beats who apparently lack basic knowledge about what these companies do and their roles in perpetuating — not fighting — identity theft.

It seems to me that some of the world’s most influential publications have for too long given Equifax and the rest of the credit reporting industry a free pass — perhaps because of the complexities involved in succinctly explaining the issues to consumers. Indeed, I would argue the mainstream media has largely failed to hold these companies’ feet to the fire over a pattern of lax security and a complete disregard for securing the very sensitive consumer data that drives their core businesses.

To be sure, Equifax has dug themselves into a giant public relations hole, and they just keep right on digging. On Sept. 8, I published a story equating Equifax’s breach response to a dumpster fire, noting that it could hardly have been more haphazard and ill-conceived.

But I couldn’t have been more wrong. Since then, Equifax’s response to this incident has been even more astonishingly poor.


On Tuesday, the official Equifax account on Twitter replied to a tweet requesting the Web address of the site that the company set up to give away its free one-year of credit monitoring service. That site is, but the company’s Twitter account told users to instead visit securityequifax2017[dot]com, which is currently blocked by multiple browsers as a phishing site.



Under intense public pressure from federal lawmakers and regulators, Equifax said that for 30 days it would waive the fee it charges for placing a security freeze on one’s credit file (for more on what a security freeze entails and why you and your family should be freezing their files, please see The Equifax Breach: What You Should Know).

Unfortunately, the free freeze offer from Equifax doesn’t mean much if consumers can’t actually request one via the company’s freeze page; I have lost count of how many comments have been left here by readers over the past week complaining of being unable to load the site, let alone successfully obtain a freeze. Instead, consumers have been told to submit the requests and freeze fees in writing and to include copies of identity documents to validate the requests.

Sen. Elizabeth Warren (D-Mass) recently introduced a measure that would force the bureaus to eliminate the freeze fees and to streamline the entire process. To my mind, that bill could not get passed soon enough.

Understand that each credit bureau has a legal right to charge up to $20 in some states to freeze a credit file, and in many states they are allowed to charge additional fees if consumers later wish to lift or temporarily thaw a freeze. This is especially rich given that credit bureaus earn roughly $1 every time a potential creditor (or identity thief) inquires about your creditworthiness, according to Avivah Litan, a fraud analyst with Gartner Inc.

In light of this, it’s difficult to view these freeze fees as anything other than a bid to discourage consumers from filing them.

The Web sites where consumers can go to file freezes at the other major bureaus — including TransUnion and Experian — have hardly fared any better since Equifax announced the breach on Sept. 7. Currently, if you attempt to freeze your credit file at TransUnion, the company’s site is relentless in trying to steer you away from a freeze and toward the company’s free “credit lock” service.

That service, called TrueIdentity, claims to allow consumers to lock or unlock their credit files for free as often as they like with the touch of a button. But readers who take the bait probably won’t notice or read the terms of service for TrueIdentity, which has the consumer agree to a class action waiver, a mandatory arbitration clause, and something called ‘targeted marketing’ from TransUnion and their myriad partners.

The agreement also states TransUnion may share the data with other companies:

“If you indicated to us when you registered, placed an order or updated your account that you were interested in receiving information about products and services provided by TransUnion Interactive and its marketing partners, or if you opted for the free membership option, your name and email address may be shared with a third party in order to present these offers to you. These entities are only allowed to use shared information for the intended purpose only and will be monitored in accordance with our security and confidentiality policies. In the event you indicate that you want to receive offers from TransUnion Interactive and its marketing partners, your information may be used to serve relevant ads to you when you visit the site and to send you targeted offers.  For the avoidance of doubt, you understand that in order to receive the free membership, you must agree to receive targeted offers.

TransUnion then encourages consumers who are persuaded to use the “free” service to subscribe to “premium” services for a monthly fee with a perpetual auto-renewal.

In short, TransUnion’s credit lock service (and a similarly named service from Experian) doesn’t prevent potential creditors from accessing your files, and these dubious services allow the credit bureaus to keep selling your credit history to lenders (or identity thieves) as they see fit.

As I wrote in a Sept. 11 Q&A about the Equifax breach, I take strong exception to the credit bureaus’ increasing use of the term “credit lock” to divert people away from freezes. Their motives for saddling consumers with even more confusing terminology are suspect, and I would not count on a credit lock to take the place of a credit freeze, regardless of what these companies claim (consider the source).

Experian’s freeze Web site has performed little better since Sept. 7. Several readers pinged KrebsOnSecurity via email and Twitter to complain that while Experian’s freeze site repeatedly returned error messages stating that the freeze did not go through, these readers’ credit cards were nonetheless charged $15 freeze fees multiple times.

If the above facts are not enough to make your blood boil, consider that Equifax and other bureaus have been lobbying lawmakers in Congress to pass legislation that would dramatically limit the ability of consumers to sue credit bureaus for sloppy security, and cap damages in related class action lawsuits to $500,000.

If ever there was an industry that deserved obsolescence or at least more regulation, it is the credit bureaus. If either of those outcomes are to become reality, it is going to take much more attentive and relentless coverage on the part of the world’s top news publications. That’s because there’s a lot at stake here for an industry that lobbies heavily (and successfully) against any new laws that may restrict their businesses.

Here’s hoping the media can get up to speed quickly on this vitally important topic, and help lead the debate over legal and regulatory changes that are sorely needed.

Sep 20 2017

Samba Releases Security Updates

Original release date: September 20, 2017

The Samba Team has released security updates to address several vulnerabilities in Samba. An attacker could exploit any of these vulnerabilities to obtain access to potentially sensitive information.

US-CERT encourages users and administrators to review the Samba Security Announcements for CVE-2017-12150, CVE-2017-12151, and CVE-2017-12163 and apply the necessary updates, or refer to their Linux or Unix-based OS vendors for appropriate patches.

This product is provided subject to this Notification and this Privacy & Use policy.