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MinIO is Vulnerable to SSE Metadata Injection via Replication Headers

High severity GitHub Reviewed Published Mar 27, 2026 in minio/minio • Updated Apr 8, 2026

Package

gomod github.com/minio/minio (Go)

Affected versions

>= 0.0.0-20240328174456-468a9fae83e9, <= 0.0.0-20260212201848-7aac2a2c5b7c

Patched versions

None

Description

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 minio_20260326212440.0.0_amd64.deb
DEB arm64 minio_20260326212440.0.0_arm64.deb
RPM amd64 minio-20260326212440.0.0-1.x86_64.rpm
RPM arm64 minio-20260326212440.0.0-1.aarch64.rpm

Container Images

# 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)

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

References

@harshavardhana harshavardhana published to minio/minio Mar 27, 2026
Published to the GitHub Advisory Database Mar 27, 2026
Reviewed Mar 27, 2026
Published by the National Vulnerability Database Mar 31, 2026
Last updated Apr 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity Low
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(10th percentile)

Weaknesses

Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Learn more on MITRE.

CVE ID

CVE-2026-34204

GHSA ID

GHSA-3rh2-v3gr-35p9

Source code

Credits

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