CVE-2024-37302: Matrix synapse Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-4mhg-xv73-xq2x
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CVSS 7.5
CWE-770
Published
Advisory Summary

CVE-2024-37302 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Matrix synapse libraries in the PyPI ecosystem. The issue involves synapse denial of service through media disk space consumption. Remediation is available by upgrading affected packages to version 1.106.

CVE-2024-37302 at a Glance

CVE Identifier CVE-2024-37302
GHSA Identifier GHSA-4mhg-xv73-xq2x
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Matrix synapse
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:H).

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 High (A:H)

How to Fix CVE-2024-37302

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-2024-37302, 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-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. 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 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. ### Patches 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. ### Workarounds Synapse deployments can currently decrease the maximum file size allowed, as well as increase request rate limits. However, this does not as effectively address the issue as a dedicated rate limit on remote media downloads. Server operators may also wish to consider putting media on a dedicated disk or volume, reducing the impact of a disk fill condition. ### References * https://en.wikipedia.org/wiki/Leaky_bucket#As_a_meter ### 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-2024-37302 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-4mhg-xv73-xq2x
NVD — CVE-2024-37302 NVD
https://nvd.nist.gov/vuln/detail/CVE-2024-37302
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-2024-286.yaml

Frequently Asked Questions

What is CVE-2024-37302?
CVE-2024-37302 is a security vulnerability in Matrix synapse involving Synapse denial of service through media disk space consumption under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Matrix synapse versions are affected?
Affected versions include releases prior to 1.106 across affected packages: matrix-synapse.
What version fixes CVE-2024-37302?
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-2024-37302?
CVE-2024-37302 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2024-37302?
CVE-2024-37302 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check PyPI dependencies for CVE-2024-37302?
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-4mhg-xv73-xq2x",
  "modified" : "2026-06-06T00:28:48Z",
  "published" : "2024-12-03T18:39:12Z",
  "aliases" : [ "CVE-2024-37302" ],
  "summary" : "Synapse denial of service through media disk space consumption",
  "details" : "### Impact\n\nSynapse 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.\n\n### Patches\n\nSynapse 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.\n\n### Workarounds\n\nSynapse deployments can currently decrease the maximum file size allowed, as well as increase request rate limits. However, this does not as effectively address the issue as a dedicated rate limit on remote media downloads.\n\nServer operators may also wish to consider putting media on a dedicated disk or volume, reducing the impact of a disk fill condition.\n\n### References\n\n* https://en.wikipedia.org/wiki/Leaky_bucket#As_a_meter\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:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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-4mhg-xv73-xq2x"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-37302"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/element-hq/synapse"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2024-286.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-12-03T18:39:12Z",
    "nvd_published_at" : "2024-12-03T17:15:10Z"
  }
}