SeaweedFS: Path traversal in the S3 gateway X-Amz-Copy-Source header allows cross-bucket object read

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.7 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS

• CVE-2026-55874: 0.61% estimated exploitation activity in the next 30 days; percentile 49.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The SeaweedFS S3 API gateway did not reject .. path segments in the X-Amz-Copy-Source header used by CopyObject and UploadPartCopy. The request URL path was hardened against traversal in 4.30 (CVE-2026-54917), but the copy-source header was only checked for emptiness, so a .. segment in the copy source survived into the server-side filer path and resolved into a different bucket. Impact A confused-deputy authorization bypass that breaks bucket isolation. IAM evaluates the caller's policy against the bucket named in the request URL (the destination the caller owns), while the copy reads its source from the traversed target bucket. An identity scoped to a single bucket (Read + Write on one bucket it controls) can therefore read any object in any bucket on the instance and land the result in its own bucket. For example, a caller authorized only for bucket-a issues a CopyObject into bucket-a with copy source bucket-a/../<victim-bucket/<key; the gateway reads <victim-bucket/<key…

Published by the source

28 Aug 2026, 22:17 UTC

Last modified by the source

2 Sep 2026, 19:55 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-56wq-x3wv-3ff4

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6327

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-56wq-x3wv-3ff4

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# Patch Next advisory brief: CVE-2026-55874

Advisory: SeaweedFS: Path traversal in the S3 gateway X-Amz-Copy-Source header allows cross-bucket object read
IDs: CVE-2026-55874, GHSA-56wq-x3wv-3ff4
Record: https://patchnext.com/advisories/cve-2026-55874 (revision 3, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/seaweedfs/seaweedfs 0.0.0-20260612000715-b44cf51fe931. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/seaweedfs/seaweedfs: affected < 0.0.0-20260612000715-b44cf51fe931; fixed in 0.0.0-20260612000715-b44cf51fe931

## Suggested inspection (read-only)
- Go github.com/seaweedfs/seaweedfs: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/seaweedfs/seaweedfs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-56wq-x3wv-3ff4 (OSV record GHSA-56wq-x3wv-3ff4 lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260612000715-b44cf51fe931 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6327 (OSV record GO-2026-6327 lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260612000715-b44cf51fe931 (fixed))
- Verified: https://github.com/advisories/GHSA-56wq-x3wv-3ff4 (GitHub-reviewed advisory GHSA-56wq-x3wv-3ff4 lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260612000715-b44cf51fe931)

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