PYSEC-2026-1615 Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders

Impact In Synapse versions before 1.120.1, enabling the dynamicthumbnails 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...

Synapse pagination Denial of Service

Impact In federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients. Clients could therefore fail to display room history. Patches Update to Synapse 1.152.1 or later. Workarounds There are no known workaround...

CVE-2022-41952

Synapse before 1.52.0 with URL preview functionality enabled will attempt to generate URL previews for media stream URLs without properly limiting connection time. Connections will only be terminated after maxspidersize default: 10M bytes have been downloaded, which can in some cases lead to...

Synapse vulnerable to federation denial of service via malformed events

Impact A malicious server can craft events with a depth outside the integer range allowed by Canonical JSON. When such an event is received by Synapse version up to 1.127.0, it prevents it from federating with other servers. The vulnerability has been exploited in the wild. Patches Fixed in Synap...