What’s Vulnerable › Vulnerabilities
CVE-2024-53863: Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders
- Severity: critical (CVSS 9.1 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.6% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2024-12-03 · updated 2026-06-17
- Weakness: CWE-434
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.
Affected products
- matrix-org synapse: before 1.120.1 — fixed in 1.120.1
How to fix
Upgrade to a fixed version: matrix-org synapse 1.120.1. Check the vendor advisory for mitigations.
References
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