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What You Need to Know About Arbitrary Code Execution Vulnerabilities

Despite their rather innocuous name, ACE vulnerabilities can appear in just about any software. So here's what to do...

Alan Zeichick

February 12, 2019

3 Min Read

They're serious. Notices about arbitrary code execution (ACE) vulnerabilities appear just about every week in alerts from US-CERT — the United States Computer Emergency Readiness Team, a part of the Dept. of Homeland Security. And despite their rather innocuous name, ACE can appear in just about any software.

Recently, US-CERT has warned about ACE vulnerabilities in the Android operating system, NVIDIA device drivers, Apple's IOKit and WebKit code libraries, Adobe' Acrobat Reader, Cisco's SD-WAN solution and Webex conferencing clients, McAfee Total Protection security suite, Google's Chrome, the Kubernetes container management system, and lots more besides.

In a quick examination of some vulnerability databases, I found 19,957 reports of arbitrary code execution vulnerabilities -- so it's not something rare or unusual. So what the heck is this vulnerability, and what can you do about it?

Let's take this one piece at a time. A vulnerability is a weakness in software code that could potentially lead to an exploit by a clever hacker. Just because there's a vulnerability doesn't mean that hackers know how to take advantage of it, and even if a hacker could potentially use that vulnerability, that doesn't mean that there's been a successful attack.

Those weaknesses could be caused by a simple coding error, or by failure by the software designers to imagine all the possible ways that a bad actor could subvert the system. Some vulnerabilities are easy to fix by updating the code; some require a redesign of the software; and others are best caught by anti-malware products running on the server.

Arbitrary code means malicious software code that is written by the hacker, and which generally does bad things. It might open a backdoor into a computer system, or steal vital data (like passwords), or turn off security protections, or turn the computer into a zombie that can be used to launch attacks on other computers. And finally, the arbitrary code execution vulnerability means that somehow, the bad actor could upload that malicious code onto the remote computer, by exploiting a vulnerability, and then trick the remote computer into executing, or running that code. In that case, the hacker is said to have created an arbitrary code execution exploit.

The techniques used to upload the malicious code onto the remote computer, often called injection, can be extremely sophisticated. The hacker might overwrite parts of the original program's file that's stored in memory. It might take advantage of flaws in operating systems or even microprocessors to sneak the malware into buffers or caches, and then the bad software is run automatically.

Here's what enterprises and consumers can do about arbitrary code execution vulnerabilities in commercial software:

  • Be aware. Subscribe to alerts from US-CERT or other agencies, and check to see if any of your software has a new vulnerability of any sort.

  • Install patches and fixes immediately to all of your software, especially if US-CERT or other agencies report that the vulnerability is high priority. ACE vulnerabilities sometimes fall into that category, but not always.

  • Keep your anti-malware products up to date as well, because even if the vulnerability software hasn't been patched yet, anti-malware can sometimes detect and block arbitrary code execution exploits.

  • If your software has a high-priority ACE vulnerability, consider stopping use of that software until it is patched. If patches seem to take too long to appear (say, more than a couple of weeks), complain to the software vendor.

Remember, a vulnerability is a weakness. It doesn't necessarily mean that you've been hacked, so don't overreact to an ACE warning report. However, ACE vulnerabilities can be serious, especially the longer they go unpatched, because more and more hackers may choose to exploit them. So, stay on top of those patches and fixes, okay?

Alan Zeichick is principal analyst at Camden Associates, a technology consultancy in Phoenix, Arizona, specializing in enterprise networking, cybersecurity, and software development. Follow him @zeichick.

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