How severe is CVE-2024-37302?

CVE-2024-37302 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2024-37302 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-37302?

CVE-2024-37302 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2024-37302?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2024-37302 have an EU (EUVD) identifier?

Yes. CVE-2024-37302 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3424.

When was CVE-2024-37302 published?

CVE-2024-37302 was published on 2024-12-03 and last updated on 2026-06-17.

CVE-2024-37302

CVE-2024-37302 is a high-severity vulnerability in Matrix Synapse with a CVSS 3.x base score of 7.5. 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-3424
Weakness: CWE-770
Affected product: Matrix Synapse
Published: 2024-12-03
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2024-37302?: 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.
How severe is CVE-2024-37302?: CVE-2024-37302 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2024-37302 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-37302?: CVE-2024-37302 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2024-37302?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2024-37302 have an EU (EUVD) identifier?: Yes. CVE-2024-37302 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3424.
When was CVE-2024-37302 published?: CVE-2024-37302 was published on 2024-12-03 and last updated on 2026-06-17.

References

https://github.com/element-hq/synapse/security/advisories/GHSA-4mhg-xv73-xq2x

Affected products (1)

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

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