A critical security flaw dubbed CVE-2023-20065 affects Cisco’s widely used IOS XE Software, specifically its IOx application hosting subsystem. This vulnerability could let an authenticated, local attacker break out of the application container and run commands as root—giving them total control over the underlying device. If a hacker targets a device with this bug, it could mean full system compromise. Let’s break down the problem, see how the exploit works, walk through key code snippets, and learn how to stay protected.

What is IOx in Cisco IOS XE?

Cisco’s IOx is a framework allowing third-party applications to run alongside the router’s main software (IOS XE). Think of it as lightweight containers or virtual machines running your custom code within a managed environment.

What is CVE-2023-20065, In Simple Terms?

> *CVE-2023-20065 is a vulnerability that lets attackers break out from their confined application container (sandbox) and take over the actual operating system as root (the highest privilege user) on devices running the affected Cisco IOS XE Software.*

– In Cisco’s own words

> “This vulnerability is due to insufficient restrictions on the hosted application. An attacker could exploit this vulnerability by logging in to and then escaping the Cisco IOx application container. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with root privileges.”

*Reference: Cisco Security Advisory – cisco-sa-iox-i-priv-esc-UfhBGv5j*

Who Can Be Affected?

- Devices running vulnerable versions of Cisco IOS XE Software with the IOx application hosting feature enabled

Gain Local Authenticated Access

The attacker logs into the device with valid user credentials (not necessarily as root, but must access the IOx environment).

Escape the IOx App Container

Due to improper restrictions, the attacker runs a command or script inside their container that “breaks out” and gets them onto the main system.

Run as Root

Once outside the container, the attacker’s code executes as root, letting them view, modify, or destroy any data, and even install persistent backdoors.

Step 1: Spin Up a Simple IOx App

Suppose we create a minimal IOx app based on a basic Linux container, which happens in Cisco’s “sandbox” infrastructure.

# Dockerfile for Example IOx App
FROM cisco/nano
USER appuser

CMD ["/bin/sh"]

After deploying your app, either via the official IOx app manager or commands like

ssh appuser@router-ip
ioxclient appssh <APP-ID>

You get a “constrained” shell inside your container.

Step 3: Exploit Weak Restrictions

Suppose the container mounting or system configuration is flawed (e.g., /proc, /dev, or certain host binaries are accessible). A common attack path is searching for binaries with the setuid bit set or privileged sockets:

Example Exploit Scenario

# While inside your application shell (in container):

# 1. Check for mount points or device files:
cat /proc/mounts

# 2. Look for suid binaries
find / -perm -u=s -type f 2>/dev/null

# 3. Try running host commands directly:
echo 'id; uname -a' > /tmp/test.sh
chmod +x /tmp/test.sh
./tmp/test.sh

If restrictions are weak, you might even be able to mount real filesystems, overwrite system binaries, or use “chroot”/“pivot_root” to escape.

Sample Container Escape Payload:
(If /host is mounted, or privileged binaries exist.)

# This will simply run a root-level command on the host if restrictions are weak.

echo 'echo pwned > /root/pwned.txt' | sudo /bin/sh

Or, if Docker-style “runC” escape is possible (less common, but relevant if standard containerization is used):

# RunC exploit example
runc exec -t --privileged /bin/bash

> Note: The specifics depend on the device’s configuration, but the core flaw is that containers can access resources they shouldn’t.

What Makes This Vulnerability Serious?

- Full Root Access: Once the attacker escapes, they are root on the device: they can change configs, intercept/mangle traffic, or brick the system.

Persistence: Attackers can wipe logs, install backdoors, or disrupt network traffic.

- Undetectable: All actions appear as though taken by a privileged user; normal monitoring tools may not spot the initial escape.

Is There a Patch or Mitigation?

Yes! Cisco quickly released software updates to fix this problem by tightening container restrictions and sandboxing.

- Upgrade your IOS XE to a fixed version (see official advisory).

To disable the IOx service

configure terminal
no iox
end
write memory

References and Further Reading

- Cisco Security Advisory – cisco-sa-iox-i-priv-esc-UfhBGv5j (Official)
- CVE-2023-20065 at NIST
- Cisco IOx Documentation

Conclusion

CVE-2023-20065 is a prime reminder that containerization isn’t a silver bullet. IOx’s promising features exposed a risky privilege escalation flaw, but—if you update and lock down your devices—you can stay safe. Don’t ignore security updates, always use least privilege, and monitor your devices for suspicious access.

*Stay secure: Patch early, patch often!*

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Timeline

Published on: 03/23/2023 17:15:00 UTC
Last modified on: 05/08/2023 16:15:00 UTC