The Cisco 1001-X series router doesn't look much like the one you have in your home. It's bigger and much more expensive, responsible for reliable connectivity at stock exchanges, corporate offices, your local mall, and so on. The devices play a pivotal role at institutions, in other words, including some that deal with hypersensitive information. Now, researchers are disclosing a remote attack that would potentially allow a hacker to take over any 1001-X router and compromise all the data and commands that flow through it.

And it only gets worse from there.

To compromise the routers, researchers from the security firm Red Balloon exploited two vulnerabilities. The first is a bug in Cisco’s IOS operating system—not to be confused with Apple's iOS—which would allow a hacker to remotely obtain root access to the devices. This is a bad vulnerability, but not unusual, especially for routers. It can also be fixed relatively easily through a software patch.

"It’s not a trust buoy." Ang Cui, Red Balloon

The second vulnerability, though, is much more sinister. Once the researchers gain root access, they can bypass the router's most fundamental security protection. Known as the Trust Anchor, this Cisco security feature has been implemented in almost all of the company’s enterprise devices since 2013. The fact that the researchers have demonstrated a way to bypass it in one device indicates that it may be possible, with device-specific modifications, to defeat the Trust Anchor on hundreds of millions of Cisco units around the world. That includes everything from enterprise routers to network switches to firewalls.

In practice, this means an attacker could use these techniques to fully compromise the networks these devices are on. Given Cisco's ubiquity, the potential fallout would be enormous.

“We’ve shown that we can quietly and persistently disable the Trust Anchor,” says Ang Cui, the founder and CEO of Red Balloon, who has a history of revealing major Cisco vulnerabilities. “That means we can make arbitrary changes to a Cisco router, and the Trust Anchor will still report that the device is trustworthy. Which is scary and bad, because this is in every important Cisco product. Everything.”

Dropping Anchor

In recent years, security-minded companies have increasingly added "secure enclaves" to motherboards. Different solutions go by different names: Intel has SGX, Arm has the TrustZone, Apple has the secure enclave. And Cisco has the Trust Anchor.

They variously comprise either a secure part of a computer’s regular memory, or a discrete chip—a safe, secluded oasis away from the bedlam of the computer’s main processor. No user or administrator can modify the secure enclave, no matter how much control they have over the system. Because of its immutable nature, the secure enclave can watch over and verify the integrity of everything else.

Secure-computing engineers generally view these schemes as sound in theory and productive to deploy. But in practice, it can be dangerous to rely on a sole element to act as the check on the whole system. Undermining that safeguard—which has proven possible in many companies’ implementations—strips a device of critical protections. Worse still, manipulating the enclave can make it appear that everything is fine, even when it's very much not.

That's the case with the Cisco 1001-X. The Red Balloon team showed specifically that they could compromise the device's secure boot process, a function implemented by the Trust Anchor that protects the fundamental code coordinating hardware and software as a device turns on, and checks that it's genuine and unmodified. It's a crucial way to ensure that an attacker hasn’t gained total control of a device.

On Monday, Cisco is announcing a patch for the IOS remote-control vulnerability the Red Balloon researchers discovered. And the company says it will also provide fixes for all product families that are potentially vulnerable to secure-enclave attacks like the one the researchers demonstrated. Cisco declined to characterize the nature or timing of these fixes ahead of the public disclosure. It also disputed that the secure boot vulnerability directly impacts the Trust Anchor. According to its security bulletin, all fixes are still months away from release, and there are currently no workarounds. When the patches do arrive, Cisco says, they will "require an on-premise reprogramming," meaning the fixes can't be pushed remotely, because they are so fundamental.