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.
The vulnerability results from a combination of two weaknesses (CWE-204 and CWE-307): the STS endpoint returns different error messages depending on whether the provided username exists in the LDAP directory, enabling account enumeration. At the same time, the lack of rate limiting allows an attacker to make an unlimited number of password guessing attempts against enumerated accounts. As a result, an attacker can obtain temporary STS credentials in AWS format (session tokens) that grant access to S3 resources.
An attacker can take control of LDAP user accounts in the MinIO system and obtain temporary STS tokens, resulting in unauthorized access to the victim's S3 resources (buckets and stored objects).
MinIO AIStor should be updated to version RELEASE.2026-03-17T21-25-16Z or later, in which the issue has been fixed. Additionally, it is recommended to implement external authentication attempt limiting mechanisms (e.g. at the firewall or reverse proxy level) as an additional layer of protection.
MinIO AIStor in all versions released before RELEASE.2026-03-17T21-25-16Z
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XMinio
APPMinio< 2026-03-17t21-25-16z
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