This Week In Security: VxWorks, Expensive Email Fraud, And What’s In Your Wallet?

This has been an interesting week. First off, security researchers at Armis discovered a set of serious vulnerabilities in the vxWorks Real Time Operating System (RTOS). Released under a name that sounds like the title of a western or caper movie, Urgent/11. Not familiar with vxWorks? It’s a toss-up as to whether vxWorks or Linux is more popular for embedded devices. Several printer brands, Arris modems, Sonicwall firewalls, and a whole host of other industrial and medical devices run the vxWorks RTOS.

Several of these vulnerabilities are in the network stack, rather than in applications. The worst offender is CVE-2019-12256, a vulnerability in error handling. An ICMP error response is generated from an incoming packet, and assumptions are made about that incoming packet. When data is copied from that packet into the ICMP error, the length is not first checked, allowing unconfined memory write. If this sounds familiar, it should. We covered a similar vulnerability in Apple’s XNU kernel not long ago.

This particular vulnerability can compromise a vxWorks machine even without an opened port. The saving grace of that vulnerability applies here: a maliciously crafted packet is necessarily malformed, and won’t navigate public routing. In other words, it’s LAN only, and can’t be sent over the internet.

They come in through the firewall.

A second class of vulnerability, where the name comes from, is related to the TCP urgent pointer. This rarely used TCP feature was intended to allow more up-to-date information to supersede data still being processed. Not only has TCP urgent not been widely used, the specifications were not written particularly well, with the various RFC documents describing conflicting implementations. It’s surprising that vxWorks supports it at all, but isn’t particularly surprising that their implementation is flawed. Manipulation of the data stream can cause a length integer to underflow. The nature of binary arithmetic means that underflowing an unsigned integer causes it to wrap around to maximum value, which can lead to writing packet data in the buffer in unexpected memory locations. These vulnerabilities require an established TCP connection, but the researchers describe several scenarios where that could be accomplished by an attacker.

The last RCE vulnerability they describe is in the DHCP client, ipdhcpc. This is a very simple vulnerability. One section of code allocates a buffer for DHCP options, but allocates 24 bytes fewer than the maximum size. An attacker could use this 24 byte overflow to manipulate the data structure and potentially jump execution into manipulated memory.

Update (2019-08-02 09:15 UTC-7): Hackaday received a statement from SonicWall that they made a patch for this vulnerability back on July 19th:

Ensuring the security of our customers is a responsibility we take seriously at SonicWall and we work vigilantly to always keep our customers secure. SonicWall physical firewall appliances running certain versions of SonicOS contain vulnerabilities in code utilized for remote management. At this time, there is no indication that the discovered vulnerabilities are being exploited in the wild. The patches are available now and we strongly advised our partners and end users July 19 th to apply the SonicOS patch immediately.

https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2019-0009

Capital One: What’s in Your Data

Capital One made use of Amazon AWS for storing customer data. This isn’t surprising, many companies have turned to Amazon’s seemingly inexhaustible cloud computing platform for storing large data sets. It seems, however, that Capital One failed to configure the security properly on that bucket. (As many other companies have done.) Information was leaked for over an estimated 100 million customers. A former Amazon employee has been arrested, and seems to have posted at least a portion of that data in a Github gist.

Reading between the lines, it seems that this was a very simple mistake. Perhaps credentials were leaked, or the S3 bucket was publicly available. That particular detail has not been released. There is something to be said for Capital One’s response to the incident. They were anonymously informed of the existence of the gist on July 17, using their responsible disclosure process. By the 29th, they had fixed the misconfiguration, coordinated with law enforcement, and publicly announced the breach. A twelve day turn-around is an impressive response, particularly when so many companies have tried to hide or ignore similar breaches.

Cabarrus County, NC

It seemed simple enough. The general contractor for the county’s new school building needed to update bank account information. The appropriate forms were signed and filed, and the information was updated. Nothing seemed amiss unto two months later, when the contractor notified the county that they had missed a scheduled payment of 2.5 million dollars. But the transaction went through, and the money was transferred to the account on file.

Yes, the transfer went through, but the the county had been hit with a social engineering scam. The report refers to it as an Email Account Compromise (EAC) scam, which seems to indicate that the scammer first gained access to a legitimate email account of the contractor in question. Alternatively, an attacker could simply spoof the sender’s email address, and set a different reply-to field. Unless a user was particularly watching for such a scheme, it would be easy to overlook the discrepancy. In any case, even after recovering some of the transferred money, the county seems to be out about $1.7 million. These scams are becoming more and more popular, so remember, don’t believe anything you read in an email.

The Weird and Wacky

And to round out this week’s news, yet another [Satoshi Nakamoto] candidate has been found: Linus Torvalds. While it appears to be a serious suggestion, I’ll just note that the author doesn’t have his name attached to this article. He does make one interesting observation — git is the killer blockchain app. You see, I tend to compare blockchain to the laser. Both were very clever inventions, but didn’t have any immediate uses. They were solutions in search of a problem. This article points out that core concepts of blockchain are present in git, which seems to be an accurate and clever observation. So what is blockchain good for? Git!

And the most useless security news of the week? The CAN bus on airplanes is exploitable when an attacker has unsupervised physical access. Yes, people with unsupervised physical access can do bad things to airplanes. Think about what they could do if they brought a wrench.

Reverse Engineering VxWorks (which Replaces Linux On Newer Routers)

The Linksys router seen about is a WRT54G version 1. It famously runs Linux and was the source of much hacking back in the heyday, leading to popular alternative firmware packages such as DD-WRT and Tomato. But the company went away from a Linux-based firmware starting with version 8 of the hardware. Now they are using a proprietary Real Time Operating System called VxWorks.

[Craig] recently put together a reverse engineering guide for WRT54Gv8 and newer routers. His approach is purely firmware based since he doesn’t actually own a router that runs VxWorks. A bit of poking around in the hex dump lets him identify different parts of the files, leading to an ELF header that really starts to unlock the secrets within. From there he carries out a rather lengthy process of accurately disassembling the code into something that makes sense. The tool of choice used for this is IDA Pro diassembler and debugger. We weren’t previously familiar with it, but having seen what it can do we’re quite impressed.

[Image via Wikimedia Commons]