CVE-2026-55188 in RustFS
Summary
by MITRE • 06/26/2026
RustFS is a distributed object storage system built in Rust. From 1.0.0-alpha.1 until 1.0.0-beta.9, RustFS contains an authorization bypass in the bucket replication admin API. The ListRemoteTargetHandler handler for listing remote replication targets only checks whether request credentials exist, but does not verify that the caller has replication or administrator permissions. As a result, an authenticated user with no effective bucket or admin permissions can list remote replication target configuration for a bucket. Because the returned BucketTarget objects include remote target credentials, this can disclose replication access keys and secret keys. This vulnerability is fixed in 1.0.0-beta.9.
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Analysis
by VulDB Data Team • 06/27/2026
The RustFS distributed object storage system presents a critical authorization bypass vulnerability within its bucket replication administration API that affects versions ranging from 1.0.0-alpha.1 through 1.0.0-beta.9. This flaw resides in the ListRemoteTargetHandler component which serves the purpose of enumerating remote replication targets associated with buckets. The vulnerability stems from insufficient access control validation where the system merely verifies the presence of request credentials without confirming whether the authenticated user possesses the necessary replication or administrative privileges required to perform such operations. This design oversight creates a significant security gap that allows unauthorized users to bypass intended permission controls.
The technical implementation flaw manifests in the handler's authentication logic which fails to enforce proper privilege checking mechanisms. When an authenticated user accesses the ListRemoteTargetHandler endpoint, the system performs only basic credential existence checks rather than comprehensive authorization verification. This inadequate validation process means that any user who can successfully authenticate to the system regardless of their actual permissions can retrieve information about remote replication targets. The vulnerability specifically impacts the BucketTarget objects returned by this handler which contain sensitive credential information including access keys and secret keys necessary for replication operations.
The operational impact of this authorization bypass extends beyond simple information disclosure to potentially enable more serious security compromises. An attacker with minimal privileges who can authenticate to the system gains the ability to enumerate all remote replication target configurations for buckets they do not own or manage. The disclosure of replication credentials through this vulnerability creates opportunities for unauthorized data replication, potential data exfiltration, and compromise of the entire replication infrastructure. This exposure affects the confidentiality and integrity of the storage system's replication mechanisms, potentially allowing malicious actors to establish unauthorized replication relationships with external systems.
This vulnerability aligns with CWE-284 which describes improper access control in software systems, specifically covering cases where insufficient privilege checks allow unauthorized access to protected resources. The issue also maps to ATT&CK technique T1078 which addresses valid accounts and credential access, as the vulnerability enables unauthorized access through legitimate authentication mechanisms. Additionally, it relates to T1566 which covers credential harvesting through various attack vectors, since the disclosure of replication credentials constitutes a form of credential exposure that can be exploited further. The fix implemented in version 1.0.0-beta.9 addresses this by strengthening the authorization checks within the ListRemoteTargetHandler to ensure proper privilege validation before allowing access to replication target information.
The remediation approach required for this vulnerability involves implementing comprehensive access control verification mechanisms within the bucket replication administration API. Systems administrators should immediately upgrade to version 1.0.0-beta.9 or later to receive the fixed authorization controls. Organizations utilizing RustFS should conduct thorough security assessments of their replication configurations and revoke any compromised credentials that may have been exposed through this vulnerability. Security monitoring should be enhanced to detect unauthorized access attempts to replication administration endpoints, particularly focusing on unusual enumeration patterns that might indicate exploitation attempts. The fix demonstrates proper defensive programming practices by ensuring that all administrative operations require appropriate authorization checks before granting access to sensitive configuration data, thereby preventing similar authorization bypass scenarios in other system components.