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Medium

Mastodon: Removal of integrity-protected JSON entries from signed activities

Type: advisorySources: OSV

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 threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-48028
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 16:10 UTC · Revision 1

Source evidence

Mastodon: Removal of integrity-protected JSON entries from signed activities

core-osv · Original source

Published 24 Jun 2026, 19:43 UTC

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 threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

osv:CVE-2026-48028
Complete source record
{
  "id": "7a8216422d66cef752c636cf345f44500a733807c0a9412b50e77dc3d6883e38",
  "url": "https://osv.dev/vulnerability/CVE-2026-48028",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mastodon: Removal of integrity-protected JSON entries from signed activities",
    "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 threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.",
    "evidence": "osv:CVE-2026-48028",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-48028",
      "aliases": [
        "BIT-mastodon-2026-48028",
        "CVE-2026-48028",
        "GHSA-53m7-2wrh-q839"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mastodon/mastodon",
              "type": "GIT",
              "events": [
                {
                  "introduced": "5a8ab0a3e62a8825e28bb74c1760ba6488d20c97"
                },
                {
                  "fixed": "f80b1ba92e63c3da771b405b9100f5c9abda909f"
                },
                {
                  "introduced": "12c0e58d9aa80db570fba5fa5146f3a640e99b42"
                },
                {
                  "fixed": "13b262a0c5ecba3cf10faca7eb193ca23b236af5"
                },
                {
                  "introduced": "0"
                },
                {
                  "fixed": "efb25b6aa2014201b04f25c390ad1f516a3ff52d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "4.5.0-beta.1"
                      },
                      {
                        "fixed": "4.5.10"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "4.4.0-beta.1"
                      },
                      {
                        "fixed": "4.4.17"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.3.23"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  }
                ]
              }
            }
          ],
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          "database_specific": {
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          }
        }
      ],
      "modified": "2026-10-28T02:30:30.350732190Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48028.json",
        "https://github.com/mastodon/mastodon/security/advisories/GHSA-53m7-2wrh-q839",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-48028"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-354"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48028.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-48028",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497164,
  "published_at": "2026-06-24T19:43:01.469+00:00"
}