CVE-2026-49991
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedRustFS is a distributed object storage system built in Rust. In 1.0.0-beta.4, authenticated users with only PutObject permission on their own bucket can exploit a path traversal vulnerability in the Snowball auto-extract feature to write arbitrary objects into other users' buckets, completely breaking multi-tenant isolation. The vulnerability chains three flaws: No ../ sanitization in tar entry key normalization; IAM wildcard matching uses raw (uncleaned) paths; and Filesystem path cleaning resolves ../ across bucket boundaries.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceRustFS 1.0.0-beta.4 contains a path traversal vulnerability in the Snowball auto-extract feature where authenticated users with only PutObject permission on their own bucket can write arbitrary objects to other users' buckets. The flaw chains three issues: tar entry key normalization lacks ../ sanitization, IAM wildcard matching operates on raw uncleaned paths, and filesystem path cleaning resolves ../ sequences across bucket boundaries, completely breaking multi-tenant isolation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check RustFS versionRun `rustfs --version` or inspect the installed package/version to confirm it is 1.0.0-beta.4Affected if The installed version is 1.0.0-beta.4 and has not been patched
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Verify Snowball auto-extract feature is enabledCheck the RustFS configuration for Snowball auto-extraction settings, typically found in the storage backend configuration or environment variables controlling S3 multipart upload handlingAffected if Snowball auto-extract is enabled and processing tar archives from untrusted or multi-tenant sources
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Confirm multi-tenant bucket isolation is in useInspect the RustFS deployment configuration for bucket isolation settings, looking for tenant separation or bucket boundary enforcement parametersAffected if The system hosts multiple tenants with separate buckets and relies on path-based bucket access control
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Review IAM-like permission model configurationCheck the access control configuration for S3 operations, specifically wildcard patterns applied to bucket object pathsAffected if IAM or access control policies use wildcard matching on object keys without prior path normalization
A user is affected if running RustFS 1.0.0-beta.4 with Snowball auto-extract enabled in a multi-tenant environment where bucket boundaries depend on path-based access controls.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataImplement ../ sanitization in tar entry key normalization, enforce IAM permission checks against cleaned/normalized paths, and add filesystem-layer bucket boundary enforcement to prevent cross-bucket path traversal.
- Consultation6.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,448.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-49991 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-49991 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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