CVE-2026-33419 in MinIO
Summary
by MITRE • 03/24/2026
MinIO is a high-performance object storage system. Prior to RELEASE.2026-03-17T21-25-16Z, MinIO AIStor's STS (Security Token Service) AssumeRoleWithLDAPIdentity endpoint is vulnerable to LDAP credential brute-forcing due to two combined weaknesses: (1) distinguishable error responses that enable username enumeration, and (2) absence of rate limiting on authentication attempts. An unauthenticated network attacker can enumerate valid LDAP usernames and then perform unlimited password guessing to obtain temporary AWS-style STS credentials, gaining access to the victim's S3 buckets and objects. This issue has been patched in RELEASE.2026-03-17T21-25-16Z.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/29/2026
The vulnerability identified as CVE-2026-33419 affects MinIO AIStor's Security Token Service implementation, specifically targeting the AssumeRoleWithLDAPIdentity endpoint that handles authentication against LDAP directories. This represents a critical security flaw that combines multiple weakness factors to create an exploitable condition for credential brute-forcing attacks. The vulnerability exists in versions prior to RELEASE.2026-03-17T21-25-16Z, indicating that organizations running older releases remain at risk. The security implications are severe as this flaw enables attackers to gain unauthorized access to S3 buckets and their associated objects through legitimate AWS-style temporary credentials.
The technical root cause of this vulnerability stems from two distinct but complementary weaknesses within the authentication mechanism. First, the system provides distinguishable error responses that allow attackers to enumerate valid LDAP usernames through differential analysis of authentication failure messages. This characteristic directly aligns with CWE-200, which addresses information exposure through error messages, and creates a reconnaissance vector for attackers to identify legitimate user accounts within the LDAP directory. Second, the absence of rate limiting on authentication attempts removes any barriers to conducting unlimited password guessing operations against discovered usernames. This lack of account lockout or throttling mechanisms enables brute-force attacks to proceed without restriction, making automated credential guessing highly effective.
The operational impact of this vulnerability extends beyond simple credential theft to represent a comprehensive access escalation threat. An unauthenticated network attacker can systematically enumerate valid LDAP usernames and then proceed with unlimited password guessing attempts to obtain temporary AWS-style STS credentials. Once successful, these credentials provide access to the victim's S3 buckets and all associated objects, potentially exposing sensitive data and enabling further malicious activities. The vulnerability creates a pathway for attackers to bypass traditional access controls and gain persistent access to cloud storage resources that should be protected by proper authentication mechanisms.
Organizations should immediately implement mitigation strategies to address this vulnerability. The primary solution involves upgrading to RELEASE.2026-03-17T21-25-16Z or later versions where the issue has been patched. Additionally, administrators should implement network-level protections such as firewall rules to restrict access to the STS endpoint, particularly from untrusted networks. Implementing robust rate limiting mechanisms and account lockout policies on LDAP authentication attempts would provide additional defense-in-depth measures. From an ATT&CK perspective, this vulnerability maps to techniques such as credential access through brute force and privilege escalation through valid accounts, making it a significant concern for organizations following the MITRE ATT&CK framework for threat modeling and defense planning.