CVE-2023-28434 in Minio
Summary
by MITRE • 03/22/2023
Minio is a Multi-Cloud Object Storage framework. Prior to RELEASE.2023-03-20T20-16-18Z, an attacker can use crafted requests to bypass metadata bucket name checking and put an object into any bucket while processing `PostPolicyBucket`. To carry out this attack, the attacker requires credentials with `arn:aws:s3:::*` permission, as well as enabled Console API access. This issue has been patched in RELEASE.2023-03-20T20-16-18Z. As a workaround, enable browser API access and turn off `MINIO_BROWSER=off`.
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Analysis
by VulDB Data Team • 09/09/2024
The vulnerability identified as CVE-2023-28434 affects the Minio Multi-Cloud Object Storage framework, representing a critical authorization bypass flaw that undermines the security controls designed to protect bucket-level access. This vulnerability specifically targets the `PostPolicyBucket` request processing mechanism, where an attacker can exploit a weakness in metadata validation to place objects into unauthorized buckets. The flaw exists in versions prior to RELEASE.2023-03-20T20-16-18Z, indicating that organizations running older versions of the Minio software are exposed to this risk. The vulnerability operates at the intersection of improper authorization and insecure data handling, creating a pathway for unauthorized data manipulation within the object storage environment.
The technical exploitation of this vulnerability requires an attacker to possess credentials with broad permissions including `arn:aws:s3:::*` which grants access to all buckets within the S3-compatible system. This permission level, while necessary for legitimate administrative tasks, creates a significant risk when combined with the authorization bypass mechanism. The attack vector specifically leverages crafted requests that can circumvent the metadata bucket name checking process, allowing an attacker to inject objects into any bucket regardless of their actual permissions or the bucket's intended access controls. This represents a fundamental breakdown in the access control model where the system fails to properly validate the destination bucket against the authenticated user's permissions during policy-based upload operations.
The operational impact of this vulnerability extends beyond simple unauthorized data access, as it enables potential data exfiltration, manipulation, or corruption across multiple buckets within the Minio environment. Attackers could leverage this flaw to place malicious objects into critical system buckets, potentially disrupting service availability or creating backdoor access points. The vulnerability particularly affects organizations that rely on Minio's Console API for administrative tasks, as the attack requires enabled Console API access to be effective. This creates a scenario where legitimate administrative activities become potential attack vectors, making the vulnerability particularly dangerous in environments where console access is enabled for operational purposes.
Organizations can address this vulnerability through the official patch released in RELEASE.2023-03-20T20-16-18Z, which implements proper metadata validation and authorization checks for `PostPolicyBucket` operations. The recommended workaround provides a temporary mitigation strategy by enabling browser API access while disabling the MINIO_BROWSER setting, effectively preventing the specific attack vector while maintaining operational functionality. This workaround aligns with security best practices for managing known vulnerabilities and demonstrates the importance of maintaining up-to-date security configurations. The vulnerability maps to CWE-285 (Improper Authorization) and relates to ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing) as attackers would need valid credentials to exploit the flaw, while also potentially enabling broader access to system resources. Organizations should conduct comprehensive security assessments to ensure all Minio instances are updated to patched versions and implement proper monitoring to detect unauthorized access attempts that might indicate exploitation of this vulnerability.