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Synapse denial of service through media disk space consumption

Type: advisorySources: OSV

Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are vulnerable to a disk fill attack, where an unauthenticated adversary can induce Synapse to download and cache large amounts of remote media. The default rate limit strategy is insufficient to mitigate this. This can lead to a denial of service, ranging from further media uploads/downloads failing to completely unavailability of the Synapse process, depending on how Synapse was deployed. Synapse 1.106 introduces a new "leaky bucket" rate limit on remote media downloads to reduce the amount of data a user can request at a time. This does not fully address the issue, but does limit an unauthenticated user's ability to request large amounts of data to be cached.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2024-37302
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 16:40 UTC · Revision 1

Source evidence

Synapse denial of service through media disk space consumption

core-osv · Original source

Published 3 Dec 2024, 17:04 UTC

Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are vulnerable to a disk fill attack, where an unauthenticated adversary can induce Synapse to download and cache large amounts of remote media. The default rate limit strategy is insufficient to mitigate this. This can lead to a denial of service, ranging from further media uploads/downloads failing to completely unavailability of the Synapse process, depending on how Synapse was deployed. Synapse 1.106 introduces a new "leaky bucket" rate limit on remote media downloads to reduce the amount of data a user can request at a time. This does not fully address the issue, but does limit an unauthenticated user's ability to request large amounts of data to be cached.

osv:CVE-2024-37302
Complete source record
{
  "id": "b48a7311b4e79ea6de86281285c9831f0149eb2a7c2ad92558f6ee9278a0ea26",
  "url": "https://osv.dev/vulnerability/CVE-2024-37302",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Synapse denial of service through media disk space consumption",
    "summary": "Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are vulnerable to a disk fill attack, where an unauthenticated adversary can induce Synapse to download and cache large amounts of remote media. The default rate limit strategy is insufficient to mitigate this. This can lead to a denial of service, ranging from further media uploads/downloads failing to completely unavailability of the Synapse process, depending on how Synapse was deployed. Synapse 1.106 introduces a new \"leaky bucket\" rate limit on remote media downloads to reduce the amount of data a user can request at a time. This does not fully address the issue, but does limit an unauthenticated user's ability to request large amounts of data to be cached.",
    "evidence": "osv:CVE-2024-37302",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2024-37302",
      "aliases": [
        "CVE-2024-37302",
        "GHSA-4mhg-xv73-xq2x",
        "PYSEC-2024-286"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/element-hq/synapse",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "e26673fe971a4d0316723b0e9ab487297db359f2"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.106"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.106.0rc1",
            "v1.105.0rc1",
            "v1.104.0rc1",
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-37302.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.295210697Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/37xxx/CVE-2024-37302.json",
        "https://github.com/element-hq/synapse/security/advisories/GHSA-4mhg-xv73-xq2x",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-37302"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/37xxx/CVE-2024-37302.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-37302",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504828,
  "published_at": "2024-12-03T17:04:15.839+00:00"
}