Impact

What kind of vulnerability is it? Who is impacted?

A path traversal vulnerability in MinIO's ReadMultiple internode storage-REST endpoint allows a caller holding the cluster root JWT to read files from outside the configured drive roots, bounded only by the MinIO process UID.

Distributed-erasure (multi-node) MinIO deployments are impacted. Single-node standalone deployments do not register the route and are not affected. The attack requires an HS512 JWT signed with MINIOROOTPASSWORD and carrying accessKey = MINIOROOTUSER — the same secret every peer in the cluster holds to authenticate internode traffic, so a compromised peer or any actor in possession of the root credential can mint one.

The ReadMultiple handler (cmd/storage-rest-server.go) decodes a msgpack ReadMultipleReq body containing Bucket, Prefix, and Files fields and forwards them to xlStorage.ReadMultiple (cmd/xl-storage.go) without validation:

go volumeDir := pathJoin(s.drivePath, req.Bucket) // traversal resolves here for , f := range req.Files { fullPath := pathJoin(volumeDir, req.Prefix, f) data, mt, err = s.readAllDataWithDMTime(ctx, req.Bucket, volumeDir, fullPath) }

pathJoin calls path.Clean, which resolves .. components and produces an absolute path anywhere on the filesystem — it is not a root jail. The global setRequestValidityMiddleware rejects .. in r.URL.Path and r.Form but does not inspect request bodies, so msgpack-encoded traversal bypasses it. Sibling storage methods (StatInfoFile, ReadFileHandler, ReadVersion) validate their volume argument through s.getVolDir(volume), which rejects ..; ReadMultiple skips this call.

The attacker sends POST /minio/storage/{drivePath}/v63/rmpl with a msgpack-encoded body carrying ../ sequences in the Bucket field. The server opens the resulting path via os.OpenFile with ORDONLY|ONOATIME and returns its contents in the msgpack response stream.

Impact by deployment:

- Bare-metal with User=minio in the systemd unit — the ONOATIME ownership check bounds the read to files owned by the MinIO UID. Reachable secrets include TLS private keys, KMS/KES key material, systemd credentials, and data belonging to other tenants sharing the same UID on the host. Secrets leaked this way persist across cluster credential rotation.

- Containerized running as UID 0 (the historical default for the official Docker image, docker-compose examples, and Helm charts without securityContext.runAsNonRoot) — the primitive escalates to arbitrary host-filesystem disclosure: /etc/shadow, /root/, Kubernetes service-account tokens, cloud-init metadata caches.

Affected components: cmd/storage-rest-server.go (ReadMultiple handler), cmd/xl-storage.go (xlStorage.ReadMultiple).

CWE: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory — 'Path Traversal')

CVSS v4.0 Score: 6.9 (Medium)

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Affected Versions

All MinIO releases from RELEASE.2022-07-24T01-54-52Z through the final release of the minio/minio open-source project, RELEASE.2025-09-07T16-13-09Z.

The vulnerability was introduced in commit f939d1c18 ("Independent Multipart Uploads", PR #15346), which added the ReadMultiple storage-REST endpoint as part of the multipart upload redesign. The first affected release is RELEASE.2022-07-24T01-54-52Z.

Patches

Fixed in: MinIO AIStor RELEASE.2026-04-14T21-32-45Z (recommended upgrade target). The fix — which removed the ReadMultiple handler, the corresponding storage-driver method, the msgpack datatypes, the REST-client wrapper, and the route registration — first shipped in MinIO AIStor RELEASE.2024-10-23T19-38-07Z. Every AIStor release from RELEASE.2024-10-23T19-38-07Z onward is unaffected; users should upgrade to RELEASE.2026-04-14T21-32-45Z or later to pick up the accumulated fixes and improvements shipped since.

Binary Downloads

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe |

FIPS Binaries

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips |

Package Downloads

| Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | minio20260414213245.0.0amd64.deb | | DEB | arm64 | minio20260414213245.0.0arm64.deb | | RPM | amd64 | minio-20260414213245.0.0-1.x8664.rpm | | RPM | arm64 | minio-20260414213245.0.0-1.aarch64.rpm |

Container Images

bash Standard docker pull quay.io/minio/aistor/minio:RELEASE.2026-04-14T21-32-45Z podman pull quay.io/minio/aistor/minio:RELEASE.2026-04-14T21-32-45Z

FIPS docker pull quay.io/minio/aistor/minio:RELEASE.2026-04-14T21-32-45Z.fips podman pull quay.io/minio/aistor/minio:RELEASE.2026-04-14T21-32-45Z.fips

Homebrew (macOS)

bash brew install minio/aistor/minio

Workarounds

- Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2026-04-14T21-32-45Z or later.

If upgrading is not immediately possible:

- Rotate the root credential and restrict who holds it. The exploit requires a JWT signed with MINIOROOTPASSWORD. Treat the root credential as the host-filesystem disclosure primitive that it is: rotate it after any suspected exposure, store it only in the secret manager that bootstraps the cluster, and do not hand it to applications or operators who only need object-level access.

- Do not run the MinIO container as UID 0. Set securityContext.runAsNonRoot: true (and a non-zero runAsUser) in Kubernetes manifests, or add --user to docker run. This reduces the blast radius from arbitrary host-filesystem disclosure to MinIO-UID-owned files only.

- Restrict the internode storage-REST port at the network layer. In distributed deployments, the storage-REST route is served on the same port as the S3 API by default. Where feasible, use --internode-port to expose internode traffic on a separate interface reachable only from other cluster peers, and block that interface from client networks.

Credits

- Finders: Discovered by Claude, Anthropic's AI assistant, and triaged by Adrian Denkiewicz at Doyensec in collaboration with Anthropic Research.

Resources

- Introducing commit: f939d1c18 (PR #15346) - CWE-22 — Improper Limitation of a Pathname to a Restricted Directory - CVE-2022-35919 — MinIO admin-authenticated path traversal in server-update endpoint (same class, different channel) - MinIO AIStor

MinIO is a high-performance object storage system. Starting in RELEASE.2023-05-18T00-05-36Z and prior to RELEASE.2026-04-11T03-20-12Z, an authentication bypass vulnerability in MinIO's STREAMING-UNSIGNED-PAYLOAD-TRAILER code path allows any user who knows a valid access key to write arbitrary objects to any bucket without knowing the secret key or providing a valid cryptographic signature. Any MinIO deployment is impacted. The attack requires only a valid access key (the well-known default minioadmin, or any key with WRITE permission on a bucket) and a target bucket name. PutObjectHandler and PutObjectPartHandler call newUnsignedV4ChunkedReader with a signature verification gate based solely on the presence of the Authorization header. Meanwhile, isPutActionAllowed extracts credentials from either the Authorization header or the X-Amz-Credential query parameter, and trusts whichever it finds. An attacker omits the Authorization header and supplies credentials exclusively via the query string. The signature gate evaluates to false, doesSignatureMatch is never called, and the request proceeds with the permissions of the impersonated access key. This affects PutObjectHandler (standard and tables/warehouse bucket paths) and PutObjectPartHandler (multipart uploads). Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2026-04-11T03-20-12Z or later. If upgrading is not immediately possible, block unsigned-trailer requests at the load balancer. Reject any request containing X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER at the reverse proxy or WAF layer. Clients can use STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER (the signed variant) instead. Alternatively, restrict WRITE permissions. Limit s3:PutObject grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any user with WRITE permission can exploit it with only their access key.

MinIO is a high-performance object storage system. Starting in RELEASE.2023-05-18T00-05-36Z and prior to RELEASE.2026-04-11T03-20-12Z, an authentication bypass vulnerability in MinIO's Snowball auto-extract handler (PutObjectExtractHandler) allows any user who knows a valid access key to write arbitrary objects to any bucket without knowing the secret key or providing a valid cryptographic signature. Any MinIO deployment is impacted. The attack requires only a valid access key (the well-known default minioadmin, or any key with WRITE permission on a bucket) and a target bucket name. When authTypeStreamingUnsignedTrailer support was added, the new auth type was handled in PutObjectHandler and PutObjectPartHandler but was never added to PutObjectExtractHandler. The snowball auto-extract handler's switch rAuthType block has no case for authTypeStreamingUnsignedTrailer, so execution falls through with zero signature verification. The isPutActionAllowed call before the switch extracts the access key and checks IAM permissions, but does not verify the cryptographic signature. An attacker sends a PUT request with X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER, X-Amz-Meta-Snowball-Auto-Extract: true, and an Authorization header containing a valid access key with a completely fabricated signature. The request is accepted and the tar payload is extracted into the bucket. Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2026-04-11T03-20-12Z or later. If upgrading is not immediately possible, block unsigned-trailer requests at the load balancer. Reject any request containing X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER at the reverse proxy or WAF layer. Clients can use STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER (the signed variant) instead. Alternatively, restrict WRITE permissions. Limit s3:PutObject grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any user with WRITE permission can exploit it with only their access key.

Impact

What kind of vulnerability is it? Who is impacted?

MinIO's S3 Select feature is vulnerable to memory exhaustion when processing CSV files containing lines longer than available memory. The CSV reader's nextSplit() function calls bufio.Reader.ReadBytes('\n') with no size limit, buffering the entire input in memory until a newline is found. A CSV file with no newline characters causes the entire contents to be read into a single allocation, leading to an OOM crash of the MinIO server process.

This is exploitable by any authenticated user with s3:PutObject and s3:GetObject permissions. The attack is especially practical when combined with compression: a ~2 MB gzip-compressed CSV can decompress to gigabytes of data without newlines, allowing a small upload to cause large memory consumption on the server. However, compression is not required — a sufficiently large uncompressed CSV with no newlines triggers the same issue.

Affected component: internal/s3select/csv/reader.go, function nextSplit().

CWE: CWE-770 (Allocation of Resources Without Limits or Throttling)

Affected Versions

All MinIO releases are through the final release of the minio/minio open-source project.

The vulnerability was introduced in commit https://github.com/minio/minio/commit/7c14cdb60e53dbfdad2be644dfb180cab19fffa7, which added S3 Select support for CSV. The CSV reader has used unbounded line reads since this commit (originally via Go's stdlib encoding/csv.Reader, later via bufio.Reader.ReadBytes after a refactor in PR #8200.

The first affected release is RELEASE.2018-08-18T03-49-57Z.

Patches

Fixed in: MinIO AIStor RELEASE.2025-12-20T04-58-37Z

The fix replaces the unbounded bufio.Reader.ReadBytes('\n') call with a byte-at-a-time loop that caps line scanning at 128 KB (csvSplitSize). If no newline is found within this limit, the reader returns an error instead of continuing to buffer.

Binary Downloads

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe |

FIPS Binaries

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips |

Package Downloads

| Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | minio20251220045837.0.0amd64.deb | | DEB | arm64 | minio20251220045837.0.0arm64.deb | | RPM | amd64 | minio-20251220045837.0.0-1.x8664.rpm | | RPM | arm64 | minio-20251220045837.0.0-1.aarch64.rpm |

Container Images

bash Standard docker pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z podman pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z

FIPS docker pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z.fips podman pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z.fips

Homebrew (macOS)

bash brew install minio/aistor/minio

Workarounds

- Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2025-12-20T04-58-37Z or later.

If upgrading is not immediately possible:

- Disable S3 Select access via IAM policy. Deny the s3:GetObject action with a condition restricting s3:prefix on sensitive buckets, or more specifically, deny SelectObjectContent requests at a reverse proxy by blocking POST requests with ?select&select-type=2 query parameters.

- Restrict PutObject permissions. Limit s3:PutObject grants to trusted principals to reduce the attack surface. Note: this reduces risk but does not eliminate the vulnerability since any authorized user can exploit it.

References

- Introducing commit: 7c14cdb60 (PR #6127) - MinIO AIStor

Impact

What kind of vulnerability is it? Who is impacted?

A flaw in extractMetadataFromMime() allows any authenticated user with s3:PutObject permission to inject internal server-side encryption metadata into objects by sending crafted X-Minio-Replication- headers on a normal PutObject request. The server unconditionally maps these headers to X-Minio-Internal- encryption metadata without verifying that the request is a legitimate replication request. Objects written this way carry bogus encryption keys and become permanently unreadable through the S3 API.

Any authenticated user or service with s3:PutObject permission on any bucket can make objects permanently unreadable by injecting fake SSE encryption metadata. The attacker sends a standard PutObject request with X-Minio-Replication-Server-Side-Encryption- headers but without the X-Minio-Source-Replication-Request header that marks legitimate replication traffic. The server maps these headers to internal encryption metadata (X-Minio-Internal-Server-Side-Encryption-Sealed-Key, etc.), causing all subsequent GetObject and HeadObject calls to treat the object as encrypted with keys that do not exist.

This is a targeted denial-of-service vulnerability. An attacker can selectively corrupt individual objects or entire buckets. The ReplicateObjectAction IAM permission is never checked because the request is a normal PutObject, not a replication request.

Affected component: cmd/handler-utils.go, function extractMetadataFromMime().

Affected Versions

All MinIO releases through the final release of the minio/minio open-source project.

The vulnerability was introduced in commit 468a9fae83e965ecefa1c1fdc2fc57b84ece95b0 ("Enable replication of SSE-C objects", PR #19107, 2024-03-28). The first affected release is RELEASE.2024-03-30T09-41-56Z.

Patches

Fixed in: MinIO AIStor RELEASE.2026-03-26T21-24-40Z

Binary Downloads

| Platform | Architecture | Download | | -------- | ------------ | -------- | | Linux | amd64 | minio | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe |

FIPS Binaries

| Platform | Architecture | Download | | -------- | ------------ | -------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips |

Package Downloads

| Format | Architecture | Download | | ------ | ------------ | -------- | | DEB | amd64 | minio20260326212440.0.0amd64.deb | | DEB | arm64 | minio20260326212440.0.0arm64.deb | | RPM | amd64 | minio-20260326212440.0.0-1.x8664.rpm | | RPM | arm64 | minio-20260326212440.0.0-1.aarch64.rpm |

Container Images

bash Standard docker pull quay.io/minio/aistor/minio:RELEASE.2026-03-26T21-24-40Z podman pull quay.io/minio/aistor/minio:RELEASE.2026-03-26T21-24-40Z

FIPS docker pull quay.io/minio/aistor/minio:RELEASE.2026-03-26T21-24-40Z.fips podman pull quay.io/minio/aistor/minio:RELEASE.2026-03-26T21-24-40Z.fips

Homebrew (macOS)

bash brew install minio/aistor/minio

Workarounds

Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2026-03-26T21-24-40Z or later.

If upgrading is not immediately possible:

- Restrict replication headers at a reverse proxy / load balancer. Drop or reject any request containing X-Minio-Replication-Server-Side-Encryption- headers that does not also carry X-Minio-Source-Replication-Request. This blocks the injection path without modifying the server.

- Audit IAM policies. Limit s3:PutObject grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any authorized user can exploit it.

References

- Introducing commit: 468a9fae8 (PR #19107) - MinIO AIStor

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 | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe |

FIPS Binaries

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips |

Package Downloads

| Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | minio20260317212516.0.0amd64.deb | | DEB | arm64 | minio20260317212516.0.0arm64.deb | | RPM | amd64 | minio-20260317212516.0.0-1.x8664.rpm | | RPM | 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.

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.

Impact What kind of vulnerability is it? Who is impacted?

A JWT algorithm confusion vulnerability in MinIO's OpenID Connect authentication allows an attacker who knows the OIDC ClientSecret to forge arbitrary identity tokens and obtain S3 credentials with any policy, including consoleAdmin.

An attacker with knowledge of the OIDC ClientSecret can:

- Impersonate any user identity - Obtain S3 credentials with any IAM policy, including consoleAdmin - Access, modify, or delete any data in the MinIO deployment

The attack is deterministic (100% success rate, no race conditions).

Attack Prerequisites

The attacker must know the OIDC ClientSecret. While this is a shared credential (not a private key), it is more accessible than commonly assumed:

- CVE-2023-28432 previously leaked environment variables including MINIOIDENTITYOPENIDCLIENTSECRET - Client secrets are often present in frontend OAuth configurations, mobile app bundles, CI/CD pipelines, and shared configuration files - In many organizations, the client secret is accessible to operators and engineers who should not be able to forge arbitrary identities

Affected Versions

All MinIO releases from RELEASE.2022-11-08T05-27-07Z through the final release of the minio/minio open-source project.

Patches

Fixed in: MinIO AIStor RELEASE.2026-03-17T21-25-16Z

Downloads

Binary Downloads

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe |

FIPS Binaries

| Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips |

Package Downloads

| Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | minio20260317212516.0.0amd64.deb | | DEB | arm64 | minio20260317212516.0.0arm64.deb | | RPM | amd64 | minio-20260317212516.0.0-1.x8664.rpm | | RPM | 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. - As a workaround, ensure that the OIDC ClientSecret is treated as a highly sensitive credential and is not exposed to untrusted parties.