Authenticated cross-bucket writes via multipart routing bypass
Published Mar 22, 2023 · Updated Oct 21, 2025
Privilege escalation in MinIO before RELEASE.2023-03-20T20-16-18Z allows remote authenticated users to write objects to any bucket. The API router accepted malformed Content-Type values containing multipart/form-data, routing crafted requests to PostPolicyBucket past metadata-bucket checks. Exploitation requires credentials with arn:aws:s3:::* permission and enabled Console API access, and permits unauthorized object placement across buckets.
Summary
What happened
Privilege escalation in MinIO before RELEASE.2023-03-20T20-16-18Z allows remote authenticated users to write objects to any bucket. The API router accepted malformed Content-Type values containing multipart/form-data, routing crafted requests to PostPolicyBucket past metadata-bucket checks. Exploitation requires credentials with arn:aws:s3:::* permission and enabled Console API access, and permits unauthorized object placement across buckets.
The record
- CVE
- CVE-2023-28434
- Published
- Mar 22, 2023
- Updated
- Oct 21, 2025
- Vendor
- MinIO
- Product
- MinIO
- Classifications
- CWE-269, T1565.001
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 22, 2023CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< RELEASE.2023-03-20T20-16-18Z
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- MinIO PostPolicyBucket regression testproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities catalog listingknown exploited catalog
Technologies
Your stack
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Your stack
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