CVE-2023-28433 in Minio
Summary
by MITRE • 03/22/2023
Minio is a Multi-Cloud Object Storage framework. All users on Windows prior to version RELEASE.2023-03-20T20-16-18Z are impacted. MinIO fails to filter the `\` character, which allows for arbitrary object placement across buckets. As a result, a user with low privileges, such as an access key, service account, or STS credential, which only has permission to `PutObject` in a specific bucket, can create an admin user. This issue is patched in RELEASE.2023-03-20T20-16-18Z. There are no known workarounds.
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Analysis
by VulDB Data Team • 03/23/2023
The vulnerability identified as CVE-2023-28433 represents a critical authorization bypass flaw within the MinIO object storage framework affecting Windows deployments prior to the RELEASE.2023-03-20T20-16-18Z version. This vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize the backslash character, creating a path traversal condition that allows unauthorized privilege escalation. The flaw specifically impacts environments where users possess limited permissions such as access keys, service accounts, or STS credentials with only PutObject capabilities in designated buckets. The technical implementation fails to enforce proper access controls when processing object names containing backslash characters, enabling malicious actors to manipulate object placement across bucket boundaries. This represents a significant deviation from expected security boundaries where object storage systems should maintain strict isolation between different storage units.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables privilege escalation to administrative levels through what appears to be an indirect path manipulation attack. An attacker with minimal permissions can exploit this flaw to create administrative user accounts, effectively bypassing the intended security model of the MinIO framework. This vulnerability directly violates the principle of least privilege and demonstrates a failure in the authorization enforcement mechanisms. The backslash character filtering failure creates a pathway for arbitrary object placement that circumvents normal bucket access controls, allowing attackers to place objects in locations they should not have access to. The vulnerability's exploitation does not require elevated privileges initially, making it particularly dangerous as it can be leveraged by users with basic storage permissions to gain full administrative control over the object storage system.
The root cause of this vulnerability aligns with CWE-22 Path Traversal and CWE-73 Improper Neutralization of Special Elements in Output Used by a Downstream Component, specifically manifesting as a path traversal attack that exploits improper input filtering. From an attack framework perspective, this vulnerability maps to multiple ATT&CK techniques including T1078 Valid Accounts for initial access and T1548 Abuse of Cloud Infrastructure for privilege escalation. The flaw demonstrates a critical oversight in the input sanitization process where the system fails to properly validate and sanitize user-provided object names before processing them through the storage hierarchy. This allows an attacker to craft object names that contain backslash characters which are then interpreted by the system as path separators, enabling unauthorized access to administrative functions. The vulnerability's persistence across multiple authentication methods indicates a systemic issue in the core object storage processing logic rather than a configuration-specific problem.
Organizations utilizing MinIO on Windows platforms should immediately implement the patched version RELEASE.2023-03-20T20-16-18Z to remediate this vulnerability. Due to the nature of the flaw, no effective workarounds exist that can be implemented without modifying the core application logic. System administrators should conduct immediate inventory checks to identify all affected Windows deployments and ensure proper patching across all environments. The vulnerability's potential for administrative privilege escalation makes it particularly critical to address promptly, as it could enable attackers to gain complete control over object storage systems. Security monitoring should be enhanced to detect anomalous object placement patterns that might indicate exploitation attempts, particularly around bucket boundary crossings. The incident highlights the importance of thorough input validation and proper access control enforcement in distributed storage systems, emphasizing that even seemingly simple character filtering can have profound security implications. Organizations should also review their access control policies and ensure that least privilege principles are properly enforced across all MinIO deployments to minimize the potential impact of similar vulnerabilities in the future.