CVE-2023-1786: Unveiling Sensitive Data Exposure Vulnerability in Cloud-init Logs before Version 23.1.2

In this long-read post, we'll dive deep into a vulnerability named "CVE-2023-1786" discovered in cloud-init before version 23.1.2. This vulnerability can lead to sensitive data, such as hashed passwords, being exposed in Cloud-init logs, which attackers can leverage to escalate their privileges on affected systems.

We'll explain the details of this vulnerability and provide code snippets to illustrate the issue. Additionally, we'll discuss the possible consequences of this vulnerability, provide links to original references, and touch upon the exploit details.

What is Cloud-init?

Cloud-init is an open-source package widely used across cloud providers, such as AWS and Azure, to configure and bootstrap new instances. Cloud-init allows users to handle the early initialization (metadata) and configuration of virtual machines upon the first boot, making it a critical component of cloud infrastructure.

For more information about Cloud-init, visit its official GitHub repository: https://github.com/canonical/cloud-init.

Vulnerability Explanation

The vulnerability (CVE-2023-1786) specifically affects cloud-init logs. Log files, used for logging activities on the system or within applications, can contain sensitive information. In this particular case, cloud-init logs may inadvertently expose hashed passwords due to inadequate filtering or handling of sensitive data.

An attacker who gains access to Cloud-init log data may be able to exploit this vulnerability by extracting hashed passwords and utilizing cracking tools and techniques to obtain the plain-text password, effectively escalating their privileges on the affected system.

Code Snippet Illustrating the Vulnerability

The following code snippet demonstrates an example of a password logging function, where sensitive information is left exposed due to a lack of proper filtering:

def log_password_input(username, password_hash):
    msg = "User {u} entered password hash: {p}".format(u=username, p=password_hash)
    logging.info(msg)  # Insecure logging of sensitive data

In the code above, the log_password_input function logs the username and hashed password directly into the log file. A suitable solution to the problem would be to mask or filter the sensitive data before logging, as shown in the following code snippet:

def log_password_input_secure(username, password_hash):
    msg = "User {u} entered password hash: {p}".format(u=username, p='**')
    logging.info(msg)  # Secure logging of sensitive data

Original References

When the vulnerability was discovered, official notices were released, providing all the relevant information. To find the original source and detailed explanations, follow these links:

1. Cloud-init Changelog: https://cloudinit.readthedocs.io/en/latest/topics/changelog.html
2. Cloud-init GitHub Repository: https://github.com/canonical/cloud-init
3. CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1786

Exploit Details

Although there have been no public POC (Proof-of-Concept) exploits for this vulnerability, the impact and risks on affected systems should not be underestimated. An attacker who gains access to an exposed Cloud-init log may utilize available password cracking tools such as John the Ripper or Hashcat to attempt to crack the hashed passwords.

Once an attacker successfully cracks the password hashes, they may be able to gain unauthorized access to resources on the system and potentially escalate their privileges, leading to further system compromises and data breaches.

Conclusion

In summary, the CVE-2023-1786 vulnerability can lead to sensitive data exposure in cloud-init logs. To mitigate this issue, it's essential to ensure that cloud-init is updated to version 23.1.2 or higher and that sensitive data, such as hashed passwords, is appropriately masked or filtered before logging.

Stay vigilant and keep your software up-to-date to minimize the risk of possible exploitation of this vulnerability.

Timeline

Published on: 04/26/2023 23:15:00 UTC
Last modified on: 05/08/2023 18:38:00 UTC