Security researcher finds way around Flash sandbox

Adobe has tightened up Flash but a researcher has found a way to send data to a remote server

A security researcher has found a gap in the way Adobe Systems has fortified its Flash Player for better security, which could result in data being stolen and sent to a remote server.

Billy Rios, a researcher who is a security engineer for Microsoft, published on his personal blog a way to get around Flash Player's local-within-filesystem sandbox.

The sandbox allows a Shockwave Flash (SWF) file to read local files but not send data over the network. It also prevents SWF files from making JavaScript calls or HTTP or HTTPS requests, Rios wrote.

A local file is described as one that can be referenced using "file: protocol" or a Universal Naming Convention path, Rios wrote.

But Rios found that the sandbox restrictions are actually not quite so strict. He found he could bypass the sandbox but reformatting the request, such as "file://request to a remote server." Adobe, however, limits those requests to local IP (Internet protocol) addresses and hostnames, Rios wrote.

Adobe also blacklists some protocol handlers but not all, a method that Rios considers dangerous.

"If we can find a protocol handler that hasn't been blacklisted by Adobe and allows for network communication, we win," Rios wrote.

Flash does not blacklist the "mhtml" protocol handler, which is part of Microsoft's Outlook Express application and installed on Windows systems. So a SWF file could export data by using a command, which Rios detailed in his blog.

Rios said the method is particularly effective since if the request fails, the data will still be transmitted to the attacker's server without the victim knowing.

Rios wrote that there are two lessons to be learned: First, running untrusted SWF code is dangerous and that protocol handler blacklists "are bad."

An Adobe spokeswoman said the company has reviewed Rios' blog post and logged a bug, classifying it as a "moderate" risk according to its Adobe Severity Rating System.

"An attacker would first need to gain access to the user's system to place a malicious SWF file in a directory on the local machine before being able to trick the user into launching an application that can run the SWF file natively," she wrote in an e-mail. "In the majority of use scenarios, the malicious SWF file could not simply be launched by double-clicking on it; the user would have to manually open the file from within the application itself."

Adobe and Google worked together on the security improvements in Flash. Last month, the two companies released to developers the first version of Flash that uses a sandbox. It works on Google's Chrome browser on the Windows XP, Vista and 7 operating systems.

The release is a continuation of a broad program by Adobe to improve the security of its products, which includes the introduction of a regular patching cycle timed with Microsoft's Patch Tuesday releases.

Adobe also uses a sandbox in its Reader X product, which was released in November. Reader's sandbox seals the application off from attacks designed to tamper with, for example, a computer's file system or registry. The sandbox interacts with the file system, but those communications go through a broker, which limits particular actions.

Send news tips and comments to jeremy_kirk@idg.com

Join the PC World newsletter!

Error: Please check your email address.

Tags Adobe Systemssecuritydata protection

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Jeremy Kirk

IDG News Service
Show Comments

Essentials

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?