PT-2026-35117 · Go · Github.Com/Minio/Minio

Published

2026-04-14

·

Updated

2026-04-14

CVSS v3.1

8.2

High

VectorAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Impact

What kind of vulnerability is it? Who is impacted?
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:
go
newUnsignedV4ChunkedReader(r, true, r.Header.Get(xhttp.Authorization) != "")
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).
Affected components: cmd/object-handlers.go (PutObjectHandler), cmd/object-multipart-handlers.go (PutObjectPartHandler).

Affected Versions

All MinIO releases through the final release of the minio/minio open-source project.
The vulnerability was introduced in commit 76913a9fd ("Signed trailers for signature v4", PR #16484), which added authTypeStreamingUnsignedTrailer support. The first affected release is RELEASE.2023-05-18T00-05-36Z.

Patches

Fixed in: MinIO AIStor RELEASE.2026-04-11T03-20-12Z

Binary Downloads

PlatformArchitectureDownload
Linuxamd64minio
Linuxarm64minio
macOSarm64minio
macOSamd64minio
Windowsamd64minio.exe

FIPS Binaries

PlatformArchitectureDownload
Linuxamd64minio.fips
Linuxarm64minio.fips

Package Downloads

FormatArchitectureDownload
DEBamd64[minio 20260411032012.0.0 amd64.deb](https://dl.min.io/aistor/minio/release/linux-amd64/minio 20260411032012.0.0 amd64.deb)
DEBarm64[minio 20260411032012.0.0 arm64.deb](https://dl.min.io/aistor/minio/release/linux-arm64/minio 20260411032012.0.0 arm64.deb)
RPMamd64[minio-20260411032012.0.0-1.x86 64.rpm](https://dl.min.io/aistor/minio/release/linux-amd64/minio-20260411032012.0.0-1.x86 64.rpm)
RPMarm64minio-20260411032012.0.0-1.aarch64.rpm

Container Images

bash
# Standard
docker pull quay.io/minio/aistor/minio:RELEASE.2026-04-11T03-20-12Z
podman pull quay.io/minio/aistor/minio:RELEASE.2026-04-11T03-20-12Z

# FIPS
docker pull quay.io/minio/aistor/minio:RELEASE.2026-04-11T03-20-12Z.fips
podman pull quay.io/minio/aistor/minio:RELEASE.2026-04-11T03-20-12Z.fips

Homebrew (macOS)

bash
brew install minio/aistor/minio

Workarounds

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.
  • 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.

Credits

  • Finder: Arvin Shivram of Brutecat Security (@ddd)

Fix

Improper Authentication

Found an issue in the description? Have something to add? Feel free to write us 👾
dbugs@ptsecurity.com

Weakness Enumeration

CWE-287

Related Identifiers

GHSA-HV4R-MVR4-25VW

Affected Products

Github.Com/Minio/Minio