MinIO LDAP login brute-force via user enumeration and missing rate limit

### Impact _What kind of vulnerability is it? Who is impacted?_ 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. All deployments with LDAP configured running an affected version are impacted. There are two vulnerabilities: 1. User Enumeration via Distinguishable Error Messages (CWE-204) 2. Missing Rate Limiting on STS Authentication Endpoints (CWE-307) When exploited together, an attacker can: 1. Enumerate valid LDAP usernames by observing error message differences. 3. Perform high-speed password brute-force attacks against confirmed valid users. 4. Upon finding valid credentials, obtain temporary AWS-style STS credentials (`AccessKeyId`, `SecretAccessKey`, `SessionToken`) with full access to the victim user's S3 resources. ### Affected Versions All MinIO releases through the final release of the minio/minio open-source project. ### Patches **Fixed in**: MinIO AIStor RELEASE.2026-03-17T21-25-16Z #### Binary Downloads | Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | [minio](https://dl.min.io/aistor/minio/release/linux-amd64/minio) | | Linux | arm64 | [minio](https://dl.min.io/aistor/minio/release/linux-arm64/minio) | | macOS | arm64 | [minio](https://dl.min.io/aistor/minio/release/darwin-arm64/minio) | | macOS | amd64 | [minio](https://dl.min.io/aistor/minio/release/darwin-amd64/minio) | | Windows | amd64 | [minio.exe](https://dl.min.io/aistor/minio/release/windows-amd64/minio.exe) | #### FIPS Binaries | Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | [minio.fips](https://dl.min.io/aistor/minio/release/linux-amd64/minio.fips) | | Linux | arm64 | [minio.fips](https://dl.min.io/aistor/minio/release/linux-arm64/minio.fips) | #### Package Downloads | Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | [minio_20260317212516.0.0_amd64.deb](https://dl.min.io/aistor/minio/release/linux-amd64/minio_20260317212516.0.0_amd64.deb) | | DEB | arm64 | [minio_20260317212516.0.0_arm64.deb](https://dl.min.io/aistor/minio/release/linux-arm64/minio_20260317212516.0.0_arm64.deb) | | RPM | amd64 | [minio-20260317212516.0.0-1.x86_64.rpm](https://dl.min.io/aistor/minio/release/linux-amd64/minio-20260317212516.0.0-1.x86_64.rpm) | | RPM | arm64 | [minio-20260317212516.0.0-1.aarch64.rpm](https://dl.min.io/aistor/minio/release/linux-arm64/minio-20260317212516.0.0-1.aarch64.rpm) | #### Container Images ```bash # Standard docker pull quay.io/minio/aistor/minio:RELEASE.2026-03-17T21-25-16Z podman pull quay.io/minio/aistor/minio:RELEASE.2026-03-17T21-25-16Z # FIPS docker pull quay.io/minio/aistor/minio:RELEASE.2026-03-17T21-25-16Z.fips podman pull quay.io/minio/aistor/minio:RELEASE.2026-03-17T21-25-16Z.fips ``` #### Homebrew (macOS) ```bash brew install minio/aistor/minio ``` ### Workarounds - [Users of the open-source `minio/minio` project should upgrade to MinIO AIStor `RELEASE.2026-03-17T21-25-16Z` or later.](https://docs.min.io/enterprise/aistor-object-store/upgrade-aistor-server/community-edition/) If upgrading is not immediately possible: - **Network-level rate limiting**: Use a reverse proxy (e.g., nginx, HAProxy) or WAF to rate-limit requests to the `/?Action=AssumeRoleWithLDAPIdentity` endpoint. - **Firewall restrictions**: Restrict access to the STS endpoint to trusted networks/IP ranges only. - **LDAP account lockout**: Configure account lockout policies on the LDAP server itself (e.g., Active Directory lockout threshold). Note: this protects against brute-force but not enumeration, and may cause denial-of-service for legitimate users.

Source published

20 Mar 2026 20:47:54 UTC

Source modified

8 Oct 2026 08:11:01 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · 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

Publisher rating · CRITICAL