Arbitrary file upload in Element-Hq Synapse

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.

Vulnerability class: Unrestricted File Upload

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.006 (46.9th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2024-53863: held from 0.006 to 0.006.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: -0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2024-53863?
CVE-2024-53863 is a critical-severity vulnerability in Element-Hq Synapse, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.1/10. Published 2024-12-03.
How severe is CVE-2024-53863?
Critical severity. CVSS v3 base score is 9.1 out of 10.