How severe is CVE-2024-53863?

CVE-2024-53863 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2024-53863 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-53863?

CVE-2024-53863 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2024-53863?

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

Does CVE-2024-53863 have an EU (EUVD) identifier?

Yes. CVE-2024-53863 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3513.

When was CVE-2024-53863 published?

CVE-2024-53863 was published on 2024-12-03 and last updated on 2026-06-17.

CVE-2024-53863

CVE-2024-53863 is a critical-severity vulnerability in Matrix Synapse with a CVSS 3.x base score of 9.1. 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-434.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v4: 8.2
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-3513
Weakness: CWE-434
Affected product: Matrix Synapse
Published: 2024-12-03
Last modified: 2026-06-17

Description

Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP. This vulnerability is fixed in 1.120.1.

Frequently asked questions

What is CVE-2024-53863?: Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP. This vulnerability is fixed in 1.120.1.
How severe is CVE-2024-53863?: CVE-2024-53863 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2024-53863 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-53863?: CVE-2024-53863 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2024-53863?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2024-53863 have an EU (EUVD) identifier?: Yes. CVE-2024-53863 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-3513.
When was CVE-2024-53863 published?: CVE-2024-53863 was published on 2024-12-03 and last updated on 2026-06-17.

References

https://github.com/element-hq/synapse/security/advisories/GHSA-vp6v-whfm-rv3g

Affected products (1)

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

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