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GHSA-V56R-HWV5-MXG6

Vulnerability from github – Published: 2025-03-27 18:02 – Updated: 2025-10-24 19:32
VLAI
Summary
Synapse vulnerable to federation denial of service via malformed events
Details

Impact

A malicious server can craft events with a depth outside the integer range allowed by Canonical JSON. When such an event is received by Synapse version up to 1.127.0, it prevents it from federating with other servers. The vulnerability has been exploited in the wild.

Patches

Fixed in Synapse v1.127.1.

Workarounds

Closed federation environments of trusted servers or non-federating installations are not affected.

For more information

If you have any questions or comments about this advisory, please email us at security at element.io.

Severity
7.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "matrix-synapse"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.127.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-30355"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-03-27T18:02:14Z",
    "nvd_published_at": "2025-03-27T01:15:12Z",
    "severity": "HIGH"
  },
  "details": "### Impact\nA malicious server can craft events with a `depth` outside the integer range allowed by Canonical JSON. When such an event is received by Synapse version up to 1.127.0, it prevents it from federating with other servers. The vulnerability has been exploited in the wild.\n\n### Patches\nFixed in Synapse v1.127.1.\n\n### Workarounds\nClosed federation environments of trusted servers or non-federating installations are not affected.\n\n### For more information\n\nIf you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).",
  "id": "GHSA-v56r-hwv5-mxg6",
  "modified": "2025-10-24T19:32:06Z",
  "published": "2025-03-27T18:02:14Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-30355"
    },
    {
      "type": "WEB",
      "url": "https://github.com/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/element-hq/synapse"
    },
    {
      "type": "WEB",
      "url": "https://github.com/element-hq/synapse/releases/tag/v1.127.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Synapse vulnerable to federation denial of service via malformed events"
}



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