CVE-2022-4318: Exploring the Critical Vulnerability Found in cri-o Runtime Engine

Recently, a vulnerability was found in cri-o, a lightweight container runtime for Kubernetes with support for OCI (Open Container Initiative) compatible runtimes. The issue, identified as CVE-2022-4318, arises when a specially crafted environment variable is used, allowing the addition of arbitrary lines to the /etc/passwd file. This post aims to provide a detailed look at this issue, including code snippets, links to original references, and exploit details.

Vulnerability Details

The vulnerability, CVE-2022-4318, exists in cri-o's environment variable handling mechanism. It occurs when an attacker uses a specially crafted environment variable to add arbitrary lines to the /etc/passwd, thereby potentially resulting in privilege escalation, unauthorized access, or critical information disclosure.

Affected Versions

The vulnerability is present in cri-o versions 1.17.x, 1.18.x, 1.19.x, and 1.20.x.

Exploit Details

To exploit the vulnerability, an attacker crafts a custom environment variable consisting of a newline character and malicious content to be inserted into the /etc/passwd file. The content can include a new user with root privileges or unauthorized access to a specific user account.

Here's a fictitious example of a malicious environment variable that exploits the vulnerability

$ export MALICIOUS_ENV_VAR="USER_X:::root:/root:/bin/bash\nCONSTRUCTED"

Upon injection, the crafted environment variable inserts a line into the /etc/passwd file, making the attacker's controlled user have root privileges.

Mitigation

It is recommended to upgrade to cri-o version 1.21.x or newer to resolve the vulnerability. The patch for this issue primarily focuses on validating environment variables during container initialization, ensuring that invalid or maliciously crafted variables are not processed.

For more detailed information on CVE-2022-4318, please refer to the following resources

1. NVD (National Vulnerability Database) CVE-2022-4318

2. GitHub Issue #4706 in cri-o

3. GitHub cri-o PR #472: Validate environment variables

Conclusion

In conclusion, the critical vulnerability in cri-o, identified as CVE-2022-4318, allows an attacker to insert arbitrary lines into the /etc/passwd file using a specially crafted environment variable. Affected organizations and users are urged to follow the mitigation steps provided and update to the newest versions of cri-o. As always, it's essential to be diligent in keeping software up-to-date and patched to minimize potential exploitation.

Timeline

Published on: 09/25/2023 20:15:00 UTC
Last modified on: 09/26/2023 20:51:00 UTC