# CVE-2026-55874: SeaweedFS path traversal in S3 API X-Amz-Copy-Source header

Source: https://junglewise.ai/threats/cve-2026-55874-seaweedfs-path-traversal-in-s3-api-x-amz-copy-source-header  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-08. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-55874 · Severity: high · CVSS 7.7 · Published 2026-07-08

SeaweedFS is a distributed file storage system with an S3-compatible API gateway. This vulnerability allows an attacker with limited permissions (read/write access to one bucket) to read objects from any other bucket on the same instance by exploiting a path traversal flaw in the copy-object operation. The attacker can then land stolen data in their own bucket for retrieval, completely bypassing bucket isolation controls.

Technologies: [github.com/seaweedfs/seaweedfs (Go)](https://junglewise.ai/threats/technologies/github-com-seaweedfs-seaweedfs), [SeaweedFS](https://junglewise.ai/threats/technologies/seaweedfs). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [SeaweedFS](https://junglewise.ai/threats/vendors/seaweedfs).

## Quick answers

**Is CVE-2026-55874 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55874 being exploited in the wild.

**How severe is CVE-2026-55874?** High severity, with a CVSS score of 7.7, published 8 July 2026.

**Which products and versions are affected?** github.com/seaweedfs/seaweedfs (Go) < 0.0.0-20260612000715-b44cf51fe931, SEMVER:introduced=0,fixed=0.0.0-20260612000715-b44cf51fe931; SeaweedFS < 4.34.

**Is there a fix for CVE-2026-55874?** Yes. github.com/seaweedfs/seaweedfs (Go): upgrade to 0.0.0-20260612000715-b44cf51fe931 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55874 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-55874?** Check whether you run github.com/seaweedfs/seaweedfs (Go) or SeaweedFS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/seaweedfs/seaweedfs (Go): upgrade to 0.0.0-20260612000715-b44cf51fe931 or later

  ```sh
  go get github.com/seaweedfs/seaweedfs@v0.0.0-20260612000715-b44cf51fe931
  ```


## Technical details

The vulnerability is a path traversal (CWE-22) flaw in SeaweedFS's S3 API gateway. The root cause is insufficient validation of the X-Amz-Copy-Source header in CopyObject and UploadPartCopy operations. While the request URL path was hardened in version 4.30, the copy-source header was only checked for emptiness, allowing `..` segments to survive into server-side path resolution. An attacker with Low privileges (IAM permissions for a single bucket with Read+Write) can craft a CopyObject request with a copy source like `bucket-a/../victim-bucket/key`, causing the gateway to read from `victim-bucket/key` while IAM authorization is evaluated against the destination bucket the attacker controls. The same flaw affects UploadPartCopy. No user interaction is required, and the attack is network-accessible. The fix (version 4.34+) applies the same path validation guards (IsValidBucketName/IsValidObjectKey) to the copy-source header that are already used for request URLs.

## Affected products

- SeaweedFS SeaweedFS < 4.34

## Identifiers

- CVE-2026-55874
- GHSA-56wq-x3wv-3ff4
- GO-2026-6327

## Timeline

- 2026-08-28: disclosed: GitHub Advisory published
- 2026-06-12: patched: Fix committed (b44cf51fe931bd75aa4d37ae766bea90d7f85ccd)
- 2026-07-08: advisory: NVD published CVE-2026-55874

## References

- [https://api.github.com/users/47Cid](https://api.github.com/users/47Cid)
- [https://github.com/47Cid](https://github.com/47Cid)
- [https://api.github.com/users/47Cid/gists%7B/gist_id%7D](https://api.github.com/users/47Cid/gists%7B/gist_id%7D)
- [https://api.github.com/users/47Cid/repos](https://api.github.com/users/47Cid/repos)
- [https://avatars.githubusercontent.com/u/62759468?v=4](https://avatars.githubusercontent.com/u/62759468?v=4)
- [https://api.github.com/users/47Cid/events%7B/privacy%7D](https://api.github.com/users/47Cid/events%7B/privacy%7D)

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- [SeaweedFS Filer JWT authorization bypass in allowed_prefixes](https://junglewise.ai/threats/cve-2026-72921-seaweedfs-filer-jwt-authorization-bypass-in-allowed-prefixes)
- [SeaweedFS unauthenticated filer IAM gRPC service authentication bypass](https://junglewise.ai/threats/cve-2026-72920-seaweedfs-unauthenticated-filer-iam-grpc-service-authentication)
- [SeaweedFS S3 object-scope bypass in PutObjectAcl](https://junglewise.ai/threats/cve-2026-77611-seaweedfs-s3-object-scope-bypass-in-putobjectacl)
- [SeaweedFS TUS resumable-upload JWT authorization bypass](https://junglewise.ai/threats/cve-2026-77368-seaweedfs-tus-resumable-upload-jwt-authorization-bypass)