RustFS 1.0.0-beta.4 Snowball auto-extract Feature path traversal

Summaryinfo

A vulnerability marked as critical has been reported in RustFS 1.0.0-beta.4. The affected element is an unknown function of the component Snowball auto-extract Feature. This manipulation causes path traversal. This vulnerability appears as CVE-2026-49991. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in RustFS 1.0.0-beta.4 and classified as critical. Affected by this vulnerability is an unknown code of the component Snowball auto-extract Feature. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

RustFS 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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-49991 since 06/02/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/26/2026). MITRE ATT&CK project uses the attack technique T1006 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• RustFS

Version

• 1.0.0-beta.4

Website

• Product: https://github.com/rustfs/rustfs/

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