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.
For a list of image formats, as well as decoding libraries and helper programs used, see the Pillow documentation.
Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP.
If you have any questions or comments about this advisory, please email us at security at element.io.
{ "nvd_published_at": "2024-12-03T17:15:12Z", "cwe_ids": [ "CWE-434" ], "severity": "HIGH", "github_reviewed": true, "github_reviewed_at": "2024-12-03T18:44:00Z" }