GHSA-9c4q-hq6p-c237 is a high-severity (CVSS 8.2) Improper Authentication vulnerability in github.com/minio/minio. No vendor fix is recorded yet; mitigation options are listed below.
MinIO has an Unauthenticated Object Write via Missing Signature Verification in Unsigned-Trailer Uploads
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-9c4q-hq6p-c237.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-9c4q-hq6p-c237 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/minio/minioReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Two authentication bypass vulnerabilities in MinIO's STREAMING-UNSIGNED-PAYLOAD-TRAILER code path
allow 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.
There are two vulnerabilities:
- Missing Signature Verification in PutObjectExtractHandler / Snowball (CWE-306)
- Signature Verification Bypass via Query-String Credentials (CWE-287)
Vulnerability 1 — Missing signature verification in PutObjectExtractHandler (Snowball)
When authTypeStreamingUnsignedTrailer support was added (commit 76913a9fd, PR #16484), 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.
Affected component: cmd/object-handlers.go, function PutObjectExtractHandler.
Vulnerability 2 — Signature verification bypass via query-string credentials
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.
Affected components: cmd/object-handlers.go (PutObjectHandler),
cmd/object-multipart-handlers.go (PutObjectPartHandler).
CVSS v4.0 Score: 8.8 (High)
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CWE: CWE-306 (Missing Authentication for Critical Function), CWE-287 (Improper Authentication)
Affected Versions
All MinIO releases through the final release of the minio/minio open-source project.
Both vulnerabilities were 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
| 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 | minio_20260411032012.0.0_amd64.deb |
| DEB | arm64 | minio_20260411032012.0.0_arm64.deb |
| RPM | amd64 | minio-20260411032012.0.0-1.x86_64.rpm |
| RPM | arm64 | minio-20260411032012.0.0-1.aarch64.rpm |
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
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-TRAILERat the reverse proxy or WAF layer. Clients can useSTREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER(the signed variant) instead. -
Restrict WRITE permissions. Limit
s3:PutObjectgrants 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)
References
- Introducing commit:
76913a9fd(PR #16484) - MinIO AIStor
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/minio/minio | ≥ 0.0.0-20230506025312-76913a9fd5c6 | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/minio/minio, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of github.com/minio/minio has shipped for GHSA-9c4q-hq6p-c237 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-9c4q-hq6p-c237 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-9c4q-hq6p-c237. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-9c4q-hq6p-c237 in your dependencies?
O3 Security finds GHSA-9c4q-hq6p-c237 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.