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CVE-2026-54917 – Cross-Bucket Authorization Bypass – SeaweedFS prior to v4.30

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Summary

CVE-2026-54917 is a high-severity path traversal vulnerability (CWE-22) affecting SeaweedFS, a widely-deployed distributed storage system offering S3-compatible object storage and Apache Iceberg table management. The flaw resides in the S3 API gateway and the Iceberg REST catalog gateway, and allows any unauthenticated remote attacker to read from or write to arbitrary storage buckets they are not authorized to access. The vulnerability is fixed in SeaweedFS v4.30.

Technical details

  • Root cause: Both the S3 API gateway and the Iceberg REST catalog gateway initialize their HTTP routers with mux.NewRouter().SkipClean(true), which disables URL path cleaning. As a result, .. segments embedded in a request URL survive the routing layer without being normalized.
  • Trigger condition: An attacker sends a crafted HTTP request such as GET /bucket-A/../evil-bucket/key. The router matches bucket-A as the bucket and ../evil-bucket/key as the object key. The object key is then joined into a filer path using util.JoinPath (S3 gateway) or path.Join (Iceberg gateway), which collapses the .. server-side, so the actual storage operation resolves to evil-bucket.
  • Attack vector: Network-reachable, no authentication required, no user interaction required. URL-encoded variants (%2e%2e) produce identical results. The vulnerability affects multiple captured path variables including {bucket}, {prefix}, {namespace}, and {table}.
  • Impact: An unauthenticated attacker can perform unauthorized cross-bucket reads (data exfiltration) and cross-bucket writes (data tampering or injection). In deployments with authentication enabled, the bypass breaks tenant isolation and allows access to buckets beyond any granted permissions. The CVSS 4.0 vector assigns Subsequent System Confidentiality: HIGH (SC:H) and Subsequent System Integrity: HIGH (SI:H).

Affected software

  • SeaweedFS — all versions prior to 4.30

Severity

  • CVSS 4.0 Base Score: 7.8 (HIGH)
  • Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
  • CWE: CWE-22 – Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’)

Note: NIST has not yet published a CVSS v3.1 score for this CVE as of the publication date. The CVSS 4.0 score above is sourced directly from the CVE record.

Mitigation and recommended actions

  • Immediate: Upgrade SeaweedFS to v4.30 or later. The fix introduces a validation middleware that rejects captured URL path variables containing traversal segments (..), null bytes, or embedded slashes before any handler executes.
  • If patching is not immediately feasible: Restrict network access to the SeaweedFS S3 API gateway (default port 8333) and the Iceberg REST catalog gateway using firewall rules or network-level controls to limit exposure to trusted networks only. Do not expose these interfaces directly to the internet.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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