CVE-2021-21362 Bypassing readOnly policy by creating a temporary 'mc share upload' URL

What is CVE-2021-21362?

CVE-2021-21362 is a high-severity vulnerability in minio, published on 8 Mar 2021. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

MinIO is an open-source high performance object storage service and it is API compatible with Amazon S3 cloud storage service. In MinIO before version RELEASE.2021-03-04T00-53-13Z it is possible to bypass a readOnly policy by creating a temporary 'mc share upload' URL. Everyone is impacted who uses MinIO multi-users. This is fixed in version RELEASE.2021-03-04T00-53-13Z. As a workaround, one can disable uploads with `Content-Type: multipart/form-data` as mentioned in the S3 API RESTObjectPOST docs by using a proxy in front of MinIO.

Weakness: CWE-863, CWE-285

Which versions are affected by CVE-2021-21362?

It affects 1 product.

Products include Minio Minio.

How do I fix CVE-2021-21362?

Upgrade to a fixed version.

Is CVE-2021-21362 being exploited?

There is no known exploitation of CVE-2021-21362 in the wild and no public exploit code.

Other vulnerabilities in minio

• CVE-2023-28434 MinIO Security Feature Bypass Exploited High 8.8
• CVE-2023-28432 MinIO Information Disclosure Exploited High 7.5
• CVE-2020-11012 Authentication bypass MinIO Admin API Critical 9.3
• CVE-2026-33322 MinIO: JWT Algorithm Confusion in OIDC Authentication Critical 9.2
• CVE-2026-33419 MinIO: LDAP login brute-force via user enumeration and missing rate limit Critical 9.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-hq5j-6r98-9m8v, MINI-8q66-wv8v-5pww, MINI-fgpm-38vg-2j6g.