CVE-2024-37303: Matrix synapse Synapse's Unauthenticated Writes To The Vulnerability

MODERATE
Advisory Identifier: GHSA-gjgr-7834-rhxr
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CVSS 5.3
CWE-306
Published
Advisory Summary

CVE-2024-37303 is a MODERATE (CVSS 5.3) synapse's unauthenticated writes to the vulnerability (CWE-306: Missing Authentication for Critical Function) affecting Matrix synapse libraries in the PyPI ecosystem. The issue involves synapse's unauthenticated writes to the media repository allow planting of problematic content. Remediation is available by upgrading affected packages to version 1.106.

CVE-2024-37303 at a Glance

CVE Identifier CVE-2024-37303
GHSA Identifier GHSA-gjgr-7834-rhxr
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-306: Missing Authentication for Critical Function
Affected Product Matrix synapse
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix CVE-2024-37303

To remediate this vulnerability, upgrade all affected Matrix synapse dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

matrix-synapse fixed: 1.106 
pip install matrix-synapse>=1.106
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show matrix-synapse

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2024-37303, inspect your installed packages using pip:

pip show matrix-synapse

Analyze the terminal output to locate any version of Matrix synapse in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.106), your application is affected.

Note: The pip show matrix-synapse command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-306: Missing Authentication for Critical Function, where the product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. In Matrix synapse, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Synapse before version 1.106 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository. ### Patches Synapse 1.106 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be frozen in a future release, closing the attack vector. ### Workarounds Though extremely limited, server operators can use more strict rate limits based on IP address. ### References * https://github.com/matrix-org/matrix-spec-proposals/pull/3916 ### For more information If you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).

CVE-2024-37303 Affected Matrix synapse Versions

1 component(s)
Fixed Versions:
1.106
Product / Package Ecosystem Affected Versions Fixed Version
matrix-synapse
pypi/matrix-synapse
PyPI
< 1.106
1.106

References

GitHub Advisory / Wiki ADVISORY
https://github.com/element-hq/synapse/security/advisories/GHSA-gjgr-7834-rhxr
NVD — CVE-2024-37303 NVD
https://nvd.nist.gov/vuln/detail/CVE-2024-37303
Matrix synapse Source Repository REPOSITORY
https://github.com/matrix-org/matrix-spec-proposals/pull/3916
Matrix synapse Source Repository REPOSITORY
https://github.com/element-hq/synapse
Matrix synapse Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2024-287.yaml

Frequently Asked Questions

What is CVE-2024-37303?
CVE-2024-37303 is a security vulnerability in Matrix synapse involving Synapse's unauthenticated writes to the media repository allow planting of problematic content under CWE-306: Missing Authentication for Critical Function.
Which Matrix synapse versions are affected?
Affected versions include releases prior to 1.106 across affected packages: matrix-synapse.
What version fixes CVE-2024-37303?
Upgrading to 1.106 (or the latest patched release for your respective branch) resolves the vulnerability.
Is matrix-synapse affected?
Yes, matrix-synapse is affected in releases prior to 1.106. Upgrade your dependency to 1.106 or later.
What is the CVSS score of CVE-2024-37303?
CVE-2024-37303 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2024-37303?
CVE-2024-37303 is classified under CWE-306: Missing Authentication for Critical Function (The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.).
How can I check PyPI dependencies for CVE-2024-37303?
Run the dependency tree command: 'pip show matrix-synapse'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gjgr-7834-rhxr",
  "modified" : "2026-06-06T00:29:01Z",
  "published" : "2024-12-03T18:40:01Z",
  "aliases" : [ "CVE-2024-37303" ],
  "summary" : "Synapse's unauthenticated writes to the media repository allow planting of problematic content",
  "details" : "### Impact\n\nSynapse before version 1.106 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository.\n\n### Patches\n\nSynapse 1.106 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be frozen in a future release, closing the attack vector.\n\n### Workarounds\n\nThough extremely limited, server operators can use more strict rate limits based on IP address.\n\n### References\n\n* https://github.com/matrix-org/matrix-spec-proposals/pull/3916\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).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "matrix-synapse"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.106"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/element-hq/synapse/security/advisories/GHSA-gjgr-7834-rhxr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-37303"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/matrix-org/matrix-spec-proposals/pull/3916"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/element-hq/synapse"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2024-287.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-12-03T18:40:01Z",
    "nvd_published_at" : "2024-12-03T17:15:10Z"
  }
}