Synapse Matrix has a partial room state leak via Sliding Sync

{
  "id": "2cc135bc555c768442ed1146af679fa144a69da4421b54ebe5e33dff22611dae",
  "url": "https://osv.dev/vulnerability/CVE-2024-53867",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Synapse Matrix has a partial room state leak via Sliding Sync",
    "summary": "Synapse is an open-source Matrix homeserver. The Sliding Sync feature on Synapse versions between 1.113.0rc1 and 1.120.0 can leak partial room state changes to users no longer in a room. Non-state events, like messages, are unaffected. This vulnerability is fixed in 1.120.1.",
    "evidence": "osv:CVE-2024-53867",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2024-53867",
      "aliases": [
        "CVE-2024-53867",
        "GHSA-56w4-5538-8v8h",
        "PYSEC-2026-1610"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/element-hq/synapse",
              "type": "GIT",
              "events": [
                {
                  "introduced": "932cb0a92838918fc38c233be3797adf43b8893d"
                },
                {
                  "fixed": "fe3d88b833f76742874642c119b14b788341c905"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "1.113.0rc1"
                      },
                      {
                        "fixed": "1.120.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.120.1"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-53867.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.596927855Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/53xxx/CVE-2024-53867.json",
        "https://github.com/element-hq/synapse/security/advisories/GHSA-56w4-5538-8v8h",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-53867",
        "https://github.com/matrix-org/matrix-spec-proposals/pull/4186"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-497"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/53xxx/CVE-2024-53867.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-53867",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504707,
  "published_at": "2024-12-03T16:52:01.596+00:00"
}