How severe is CVE-2024-37303?

CVE-2024-37303 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2024-37303 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-37303?

CVE-2024-37303 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2024-37303?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2024-37303 have an EU (EUVD) identifier?

Yes. CVE-2024-37303 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3472.

When was CVE-2024-37303 published?

CVE-2024-37303 was published on 2024-12-03 and last updated on 2026-06-17.

CVE-2024-37303

CVE-2024-37303 is a medium-severity vulnerability in Matrix Synapse with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-306.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (35th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-3472
Weakness: CWE-306
Affected product: Matrix Synapse
Published: 2024-12-03
Last modified: 2026-06-17

Description

Synapse is an open-source Matrix homeserver. 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. 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.

Frequently asked questions

What is CVE-2024-37303?: Synapse is an open-source Matrix homeserver. 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. 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.
How severe is CVE-2024-37303?: CVE-2024-37303 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2024-37303 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-37303?: CVE-2024-37303 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2024-37303?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2024-37303 have an EU (EUVD) identifier?: Yes. CVE-2024-37303 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3472.
When was CVE-2024-37303 published?: CVE-2024-37303 was published on 2024-12-03 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*

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