CVE-2025-30355: 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…

high7.5CVSS 3.1

AVNACLPRNUINSUCNINAH

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 workarounds are available.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
debian	matrix-synapse	< matrix-synapse 1.121.0-6 (forky)	matrix-synapse 1.121.0-6 (forky)
element-hq	synapse	< 1.127.1	1.127.1
matrix	synapse	< 1.127.1	1.127.1

CVSS provenance

nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

osv7.5HIGH

vulncheck7.1HIGH