Flaw in Intel CPUs could help attackers defeat ASLR exploit defense

The branch target buffer mechanism in Intel Haswell CPUs can be used to leak ASLR memory addresses

A feature in Intel's Haswell CPUs can be abused to reliably defeat an anti-exploitation technology that exists in all major operating systems, researchers have found.

The technique, developed by three researchers from State University of New York at Binghamton and the University of California in Riverside, can be used to bypass address space layout randomization (ASLR) and was presented this week at the 49th annual IEEE/ACM International Symposium on Microarchitecture in Taipei.

ASLR is a security mechanism used by operating systems to randomize the memory addresses used by key areas of processes, so that attackers don't know where to inject their exploit shellcode.

ASLR is used to prevent memory corruption bugs, such as stack and heap overflows, from arbitrary code execution as opposed to crashes. Once such a vulnerability is exploited, the malicious code needs to be injected at a position in memory where the target process or the OS kernel itself will execute as part of normal operation.

In their paper, the three researchers show that the branch target buffer (BTB), a caching mechanism used by the CPU's branch target predictor, can be leveraged to leak ASLR addresses by triggering BTB collisions between different user processes or processes and the kernel. The branch prediction mechanism is used in modern CPUs to optimize performance.

"The BTB stores target addresses of recently executed branch instructions, so that those addresses can be obtained directly from a BTB lookup to fetch instructions starting at the target in the next cycle," the researchers explain in their paper. "Since the BTB is shared by several applications executing on the same core, information leakage from one application to another through the BTB side-channel is possible."

The researchers demonstrated their BTB-based ASLR bypass on a computer equipped with an Intel Haswell microarchitecture CPU and running a recent Linux kernel (version 4.5). Their attack can reliably recover kernel ASLR using BTB collisions in around 60 milliseconds.

The research paper proposes both software and hardware-based mitigations that could prevent BTB-based side-channel attacks in the future or harden current ASLR implementations.

Attackers currently have other methods of bypassing ASLR, but they typically require finding additional memory leak vulnerabilities and chaining those together with the original memory corruption flaw. Due to software security improvements in recent years, most remote code execution attacks today require the use of chained exploits.

Intel didn't immediately respond to a request for comments.

Join the PC World newsletter!

Error: Please check your email address.

Tags intel

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.

Lucian Constantin

IDG News Service
Show Comments

Essentials

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

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

Learn more >

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

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?