GHSA-56WQ-X3WV-3FF4
Vulnerability from github – Published: 2026-08-28 22:17 – Updated: 2026-08-28 22:17Summary
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> and writes it to the attacker-controlled destination, from which the caller reads it normally. UploadPartCopy (CopyObjectPartHandler) is affected by the same vector.
Affected versions
All releases prior to 4.34. The 4.30 fix for CVE-2026-54917 hardened the request URL path but not the X-Amz-Copy-Source header.
Patched version
4.34 and later.
Remediation
Upgrade to 4.34 or later. The fix validates the copy-source bucket and object key with the same IsValidBucketName / IsValidObjectKey guards already applied to the request URL, rejecting traversal segments before the handler runs, and applies the same check to UploadPartCopy.
Workaround
No configuration workaround. For deployments that cannot upgrade immediately, front the gateway with a reverse proxy that rejects requests whose X-Amz-Copy-Source header contains .., %2e%2e, or backslash sequences.
References
- Fix: https://github.com/seaweedfs/seaweedfs/pull/9929 (commit b44cf51fe931bd75aa4d37ae766bea90d7f85ccd)
Credit
Reported responsibly by @47Cid.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/seaweedfs/seaweedfs"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.0.0-20260612000715-b44cf51fe931"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-55874"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-28T22:17:33Z",
"nvd_published_at": "2026-07-08T15:16:30Z",
"severity": "HIGH"
},
"details": "### Summary\nThe 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.\n\n### Impact\nA confused-deputy authorization bypass that breaks bucket isolation. IAM evaluates the caller\u0027s 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.\n\nFor example, a caller authorized only for `bucket-a` issues a `CopyObject` into `bucket-a` with copy source `bucket-a/../\u003cvictim-bucket\u003e/\u003ckey\u003e`; the gateway reads `\u003cvictim-bucket\u003e/\u003ckey\u003e` and writes it to the attacker-controlled destination, from which the caller reads it normally. `UploadPartCopy` (CopyObjectPartHandler) is affected by the same vector.\n\n### Affected versions\nAll releases prior to 4.34. The 4.30 fix for CVE-2026-54917 hardened the request URL path but not the `X-Amz-Copy-Source` header.\n\n### Patched version\n4.34 and later.\n\n### Remediation\nUpgrade to 4.34 or later. The fix validates the copy-source bucket and object key with the same `IsValidBucketName` / `IsValidObjectKey` guards already applied to the request URL, rejecting traversal segments before the handler runs, and applies the same check to `UploadPartCopy`.\n\n### Workaround\nNo configuration workaround. For deployments that cannot upgrade immediately, front the gateway with a reverse proxy that rejects requests whose `X-Amz-Copy-Source` header contains `..`, `%2e%2e`, or backslash sequences.\n\n### References\n- Fix: https://github.com/seaweedfs/seaweedfs/pull/9929 (commit b44cf51fe931bd75aa4d37ae766bea90d7f85ccd)\n\n### Credit\nReported responsibly by [@47Cid](https://github.com/47Cid).",
"id": "GHSA-56wq-x3wv-3ff4",
"modified": "2026-08-28T22:17:33Z",
"published": "2026-08-28T22:17:33Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/seaweedfs/seaweedfs/security/advisories/GHSA-56wq-x3wv-3ff4"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55874"
},
{
"type": "WEB",
"url": "https://github.com/seaweedfs/seaweedfs/pull/9929"
},
{
"type": "WEB",
"url": "https://github.com/seaweedfs/seaweedfs/commit/b44cf51fe931bd75aa4d37ae766bea90d7f85ccd"
},
{
"type": "PACKAGE",
"url": "https://github.com/seaweedfs/seaweedfs"
},
{
"type": "WEB",
"url": "https://github.com/seaweedfs/seaweedfs/releases/tag/4.34"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "SeaweedFS: Path traversal in the S3 gateway X-Amz-Copy-Source header allows cross-bucket object read"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.