Synapse vulnerable to federation denial of service via malformed events

ImpactA 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. PatchesFixed in Synapse...

CVE-2025-30355: Improper Input Validation

Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild and has been fixed in Synapse v1.127.1. No known...

py-matrix-synapse -- federation denial of service via malformed events

element-hq/synapse developers report: A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild...