Ceph RGW SigV4 handler accepts unsigned x-amz-* headers on presigned requests, allowing privilege escalation

{
  "id": "9f4c2541eef164ca2bcc637293a9f3e85337ca5cf7e092d82d31193a7290ab50",
  "url": "https://osv.dev/vulnerability/CVE-2026-54330",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Ceph RGW SigV4 handler accepts unsigned x-amz-* headers on presigned requests, allowing privilege escalation",
    "summary": "Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the Ceph Object Gateway (RGW) SigV4 handler does not reject requests that carry x-amz-* headers absent from the signed header set, allowing anyone holding a presigned URL to attach arbitrary unsigned x-amz-* headers that RGW will honor. AWS S3 requires every x-amz-* header on a SigV4 request to be signed and rejects requests bearing additional unsigned headers, but RGW validates only the headers listed in X-Amz-SignedHeaders and ignores any extra ones, so they take effect without being covered by the signature. By adding such headers to a presigned PUT URL, an attacker can grant themselves more capabilities than the URL's signer intended and escalate their privileges. This issue is fixed in versions 20.2.4 and 19.2.6.",
    "evidence": "osv:CVE-2026-54330",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-54330",
      "aliases": [
        "BIT-ceph-2026-54330",
        "CVE-2026-54330",
        "GHSA-rmjq-ffrm-j6vj"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ceph/ceph",
              "type": "GIT",
              "events": [
                {
                  "introduced": "1680e466aab77cdf9ba07394bea664106580b32b"
                },
                {
                  "fixed": "f9fd95b4335bad6a26d7a74468f55d269e8dbef4"
                },
                {
                  "introduced": "3d911bce7d6557aa2d1826543a4a4e88981639da"
                },
                {
                  "fixed": "7f793731f1b39eb4f465e960113d2363c311b964"
                },
                {
                  "fixed": "5837aa8e60471128dbb672b0ff6f1b1feebe08a7"
                },
                {
                  "fixed": "5978c866d4a0812fbb024745c4f1e79aaecd6c6a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "19.0.0"
                      },
                      {
                        "fixed": "19.2.6"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "20.0.0"
                      },
                      {
                        "fixed": "20.2.4"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "5837aa8e60471128dbb672b0ff6f1b1feebe08a7"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "5978c866d4a0812fbb024745c4f1e79aaecd6c6a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v20.2.3",
            "v19.2.5",
            "v20.2.2-pre.ibm",
            "v20.2.1-pre.ibm.0",
            "v20.1.0-pre.ibm.2",
            "v20.1.0-pre.ibm.1",
            "v20.0.0-pre.ibm",
            "v19.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54330.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.615387435Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54330.json",
        "https://github.com/ceph/ceph/security/advisories/GHSA-rmjq-ffrm-j6vj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-54330",
        "https://github.com/ceph/ceph/commit/5837aa8e60471128dbb672b0ff6f1b1feebe08a7",
        "https://github.com/ceph/ceph/commit/5978c866d4a0812fbb024745c4f1e79aaecd6c6a"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-347"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54330.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-54330",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496696,
  "published_at": "2026-08-27T20:59:24.688+00:00"
}