Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring

{
  "id": "f0e2107073b4150731820a039b287a6a1efb9919664adb8a6fb76267db51299f",
  "url": "https://osv.dev/vulnerability/CVE-2026-46349",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring",
    "summary": "Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, Mastodon's normalization of incoming activities signed with Linked-Data Signatures does not sufficiently protect the activities from a certain class of spoofing, allowing attackers to re-arrange a valid signed JSON-LD activity from a third-party actor to have it processed differently. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.",
    "evidence": "osv:CVE-2026-46349",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-46349",
      "aliases": [
        "BIT-mastodon-2026-46349",
        "CVE-2026-46349",
        "GHSA-chgx-jx3p-rf73"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mastodon/mastodon",
              "type": "GIT",
              "events": [
                {
                  "introduced": "5a8ab0a3e62a8825e28bb74c1760ba6488d20c97"
                },
                {
                  "fixed": "f80b1ba92e63c3da771b405b9100f5c9abda909f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "4.5.0-beta.1"
                      },
                      {
                        "fixed": "4.5.10"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.5.10"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v4.5.9",
            "v4.5.8",
            "v4.5.7",
            "v4.5.6",
            "v4.5.5",
            "v4.5.4",
            "v4.5.3",
            "v4.5.2",
            "v4.5.1",
            "v4.5.0",
            "v4.5.0-rc.3",
            "v4.5.0-rc.2",
            "v4.5.0-rc.1",
            "v4.5.0-beta.2",
            "v4.5.0-beta.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-46349.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.199272749Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46349.json",
        "https://github.com/mastodon/mastodon/security/advisories/GHSA-chgx-jx3p-rf73",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-46349"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-347"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46349.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-46349",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509032,
  "published_at": "2026-06-24T19:40:35.022+00:00"
}