CVE-2026-41145

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.

Binary Downloads

FIPS Binaries

Package Downloads

Container Images

# 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)

brew install minio/aistor/minio

Workarounds

• 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.

• 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)

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:

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).

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-41145 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

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

1. What is CVE-2026-41145? CVE-2026-41145 is a high-severity improper authentication vulnerability in github.com/minio/minio (go), affecting versions >= 0.0.0-20230506025312-76913a9fd5c6, <= 0.0.0-20260212201848-7aac2a2c5b7c. No fixed version is listed yet. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-41145? CVE-2026-41145 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/minio/minio are affected by CVE-2026-41145? github.com/minio/minio (go) versions >= 0.0.0-20230506025312-76913a9fd5c6, <= 0.0.0-20260212201848-7aac2a2c5b7c is affected.
4. Is there a fix for CVE-2026-41145? No fixed version is listed for CVE-2026-41145 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-41145 exploitable, and should I be worried? Whether CVE-2026-41145 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-41145 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-41145? No fixed version is listed yet. In the interim: Keep the dependency up to date. Ensure authentication checks are present and cannot be bypassed by manipulating request parameters.