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RustFS (distributed object storage system in Rust) versions 1.0.0-alpha.56 through 1.0.0-alpha.82 fail to validate presigned POST (PostObject) policy conditions. As a result, policy constraints such as content-length-range, starts-with restrictions on form fields/object keys, and Content-Type constraints are not enforced server-side, allowing an attacker to submit a presigned POST upload that violates the intended policy and still have the object accepted and written.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
Repository is a Node.js proof-of-concept for CVE-2026-27607 / GHSA-w5fh-f8xh-5x3p affecting RustFS (S3-compatible object storage). It spins up a vulnerable RustFS container via docker compose (rustfs/rustfs:1.0.0-alpha.82) exposed on localhost:9000 with demo credentials, then uses the AWS SDK to generate presigned POST policies and performs multipart/form-data uploads to test whether RustFS enforces POST policy conditions. Key files: - compose.yaml: launches RustFS and maps 9000:9000; documents vulnerable vs fixed image tags. - presign.js: configures an S3Client pointing to http://localhost:9000 (path-style), creates bucket 'exploit-demo', generates presigned POSTs (Fields include Content-Type: text/plain; Conditions are caller-supplied), and fetches objects back (GetObject) to verify persistence and ContentType. - exploit.js (entry point): runs four demonstrations: 1) Valid upload within content-length-range. 2) Upload exceeding content-length-range (should be rejected; verifies object unchanged). 3) Key prefix restriction using starts-with on $key (attempts to override form field 'key' to 'secret/area/foo.txt' to test prefix bypass). 4) Content-Type restriction (policy expects image/png but upload uses Blob type text/plain; notes attacker could use text/html for XSS if stored/served). Overall capability: unauthorized/incorrectly validated object uploads via presigned POST policy condition bypass (size, key prefix, and/or Content-Type), with read-back verification against the same S3 endpoint.
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3 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
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