CVE-2022-24302 - Paramiko Unauthorized Information Disclosure Vulnerability: Details, Exploit, and Patch

In this article, we will discuss the details, exploit, and patch of a newly disclosed vulnerability in Paramiko (CVE-2022-24302) that could allow unauthorized information disclosure. Paramiko is a widely used Python library for SSHv2 protocol implementation, greatly simplifying the process of implementing secure SSH connections in Python applications.

Vulnerability Details

CVE ID: CVE-2022-24302
Affected versions: Paramiko before 2.10.1
Impact: Unauthorized information disclosure
Severity: Medium

The vulnerability exists in the write_private_key_file function in Paramiko, due to a race condition between the creation of the private key file and the chmod operation performed on the file, which sets the proper permissions. This race condition could potentially allow unauthorized users to access the private key file before its permissions are properly restricted, leading to the potential disclosure of sensitive information.

The vulnerable code can be found in the write_private_key_file function within the Paramiko module

def write_private_key_file(filename, key, password=None):
    """
...
"""
    with os.fdopen(
        os.open(filename, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, o600),
        "w",
    ) as f:
        os.chmod(filename, o600)
...

The os.open call creates the file with the desired permissions (o600), and immediately after, the os.chmod call is made to set the permissions. The issue arises due to a potential race condition that can occur between these two operations, allowing unauthorized access to the private key file.

Original References

1. Paramiko GitHub Repository: https://github.com/paramiko/paramiko
2. Paramiko version 2.10.1 Changelog: https://github.com/paramiko/paramiko/blob/v2.10.1/CHANGELOG.rst

Exploit

There is no known working exploit for this vulnerability at the time of writing this article. However, a successful attack would require either an attacker with local access to the system or the ability to trigger the write_private_key_file function to execute maliciously crafted code that could take advantage of the race condition.

Mitigation and Patch

The vulnerability is fixed in Paramiko version 2.10.1, which adjusts the write_private_key_file function to prevent the race condition. To protect against this vulnerability, upgrade to Paramiko version 2.10.1 or later.

pip install --upgrade paramiko

Additionally, ensure that your Python applications limit access to private key files through appropriate access controls and permissions, as well as avoiding the use of overly permissive file permissions.

Conclusion

In this article, we examined the CVE-2022-24302 vulnerability in Paramiko, which could potentially lead to unauthorized information disclosure. We discussed the vulnerability details, potential exploit scenarios, and the available patch for this issue. By upgrading to the latest version of Paramiko and maintaining proper access controls, developers can minimize the risk associated with this vulnerability.

Timeline

Published on: 03/17/2022 22:15:00 UTC
Last modified on: 05/23/2022 22:01:00 UTC