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Fencer Vulns
high 7.7

CVE-2021-21362 json

Bypassing readOnly policy by creating a temporary 'mc share upload' URL

published 2021-03-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8679

cvss
7.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

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.

Patch / fix

  • minio minio 2021-03-04t00-53-13z

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21362 updated cvss 6.5

minio: Allows bypassing readOnly policy by creating a temporary 'mc share upload' URL

  • Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/search-rhel8, rhacm2/thanos-rhel7, rhacm2/openshift-hive-rhel8, rhacm2/rcm-controller-rhel8, rhacm2/multiclusterhub-rhel8, rhacm2/search-collector-rhel9, +17 more Red Hat Openshift Container Storage 4 ocs4/mcg-rhel8-operator, ocs4/ocs-rhel8-operator, ocs4/ocs-must-gather-rhel8, ocs4/rook-ceph-rhel8-operator
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.32% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/minio/minio/pull/11682 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:P/A:N

Affected products

  • minio minio

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.