CVE-2022-2990: Buildah Information Disclosure Vulnerability

CVE-2022-2990 Overview

CVE-2022-2990 is an incorrect authorization vulnerability affecting the Buildah container engine. The flaw stems from improper handling of supplementary groups, which can lead to sensitive information disclosure or unauthorized data modification. An attacker with direct access to an affected container where supplementary groups are used to set access permissions could exploit this vulnerability by executing binary code within that container.

Critical Impact

Attackers with local access to affected containers can bypass supplementary group-based access controls, potentially gaining unauthorized access to sensitive files and the ability to modify protected data.

Affected Products

• Buildah Project Buildah (all versions prior to patch)
• Red Hat OpenShift Container Platform 4.0
• Red Hat Enterprise Linux 7.0, 8.0, and 9.0

Discovery Timeline

• 2022-09-13 - CVE-2022-2990 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-2990

Vulnerability Analysis

This vulnerability is classified under CWE-842 (Placement of User into Incorrect Group) and CWE-863 (Incorrect Authorization). The core issue lies in how Buildah handles supplementary group assignments during container execution. When a process runs within a container, Linux uses supplementary groups to determine file access permissions beyond the primary user/group ownership model.

Buildah's incorrect handling of these supplementary groups creates a scenario where the expected access control restrictions may not be properly enforced. This allows an attacker who has already gained access to a container to potentially read files or modify data that should be protected by group-based permissions.

The vulnerability requires local access to the container environment, meaning an attacker must first establish a foothold within the affected container. Once inside, they can exploit the supplementary groups misconfiguration to escalate their access rights to sensitive resources.

Root Cause

The root cause of CVE-2022-2990 is the incorrect placement of users into groups during container execution. Buildah fails to properly propagate or enforce supplementary group memberships, causing a mismatch between expected and actual access permissions. This design flaw allows processes within containers to access resources that supplementary group restrictions should have blocked.

Attack Vector

The attack vector is local, requiring the attacker to have direct access to an affected container. The exploitation scenario involves:

1. An attacker gains initial access to a container running on a vulnerable Buildah installation
2. The container uses supplementary groups to restrict access to sensitive files or directories
3. The attacker exploits the improper group handling to bypass these restrictions
4. The attacker can then read sensitive information or modify protected data

The vulnerability mechanism involves the container engine's failure to correctly establish supplementary group memberships when spawning processes. When Buildah creates a container or executes a command within one, the supplementary groups that should be associated with the process are not properly set, effectively granting broader access than intended. For detailed technical analysis of this vulnerability class in Linux containers, refer to the Bentham's Gaze research publication.

Detection Methods for CVE-2022-2990

Indicators of Compromise

• Unexpected file access events within containers where supplementary group permissions should have prevented access
• Process execution logs showing unusual group membership configurations
• Audit logs indicating file reads or modifications to resources protected by supplementary groups
• Container runtime logs showing discrepancies between expected and actual group assignments

Detection Strategies

• Monitor container runtime logs for processes executing with unexpected group memberships
• Implement file integrity monitoring on sensitive files within containers that rely on supplementary group access controls
• Use security scanning tools to identify Buildah installations running vulnerable versions
• Review container configurations for reliance on supplementary group-based access controls

Monitoring Recommendations

• Enable detailed audit logging for file access events within container environments
• Configure alerts for access attempts to files protected by supplementary group permissions
• Implement runtime security monitoring to detect anomalous container behavior
• Regularly scan container images and host systems for vulnerable Buildah versions

How to Mitigate CVE-2022-2990

Immediate Actions Required

• Update Buildah to the latest patched version available from your distribution
• Review container configurations to identify systems relying on supplementary group access controls
• Audit container access logs for any suspicious activity that may indicate exploitation
• Consider implementing additional access control mechanisms beyond supplementary groups

Patch Information

Red Hat has acknowledged this vulnerability and is tracking it via Bug Report #2121453. Organizations should apply the latest security updates from their Linux distribution to remediate this vulnerability. For Red Hat Enterprise Linux and OpenShift Container Platform users, updated packages addressing this vulnerability are available through the standard update channels.

Workarounds

• Avoid relying solely on supplementary groups for access control within containers until patched
• Implement alternative access control mechanisms such as SELinux or AppArmor policies
• Use file system ACLs as an additional layer of protection for sensitive resources
• Restrict container access to trusted users and processes only

# Verify Buildah version and check for updates
buildah --version

# On RHEL/CentOS/Fedora systems, update Buildah
sudo dnf update buildah

# Review supplementary group assignments in container configurations
buildah inspect --format '{{.OCIv1.Config.User}}' <container-name>