Authenticated arbitrary object writes via unchecked POST policy
Published Feb 25, 2026 · Updated Feb 25, 2026
Authorization bypass in RustFS 1.0.0-alpha.56 through 1.0.0-alpha.82 allows remote authenticated users to write arbitrary objects. The PostObject endpoint accepts a presigned POST policy without parsing its conditions or checking the request size, key prefix, and content type. A valid presigned POST is required; bypassed controls permit oversized or mis-keyed uploads that alter bucket content or exhaust storage.
Summary
What happened
Authorization bypass in RustFS 1.0.0-alpha.56 through 1.0.0-alpha.82 allows remote authenticated users to write arbitrary objects. The PostObject endpoint accepts a presigned POST policy without parsing its conditions or checking the request size, key prefix, and content type. A valid presigned POST is required; bypassed controls permit oversized or mis-keyed uploads that alter bucket content or exhaust storage.
The record
- CVE
- CVE-2026-27607
- Published
- Feb 25, 2026
- Updated
- Feb 25, 2026
- Vendor
- RustFS
- Product
- RustFS
- Classifications
- CWE-20, CWE-863, T1565.001, T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 25, 2026CVE publishedPublication date reported by the CVE source.
- Feb 25, 2026Record 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=>= 1.0.0-alpha.56, < 1.0.0-alpha.83
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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