CVE-2026-33419: MinIO: LDAP login brute-force via user enumeration and missing rate limit

Vulnerability summary

CVE-2026-33419 is a critical (CVSS 9.1) Observable Response Discrepancy vulnerability in minio. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.9% of scored vulnerabilities.

Timeline

1. 24-03-2026
   PublishedVulnerability first disclosed.
2. 25-03-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-204Observable Response DiscrepancyThe product provides different responses to incoming requests in a way that reveals internal state information to an unauthorized actor outside of the intended control sphere.
• CWE-307Improper Restriction of Excessive Authentication AttemptsThe product does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame.