Event Manipulation Vulnerability in Synapse Matrix Homeserver
CVE-2025-30355

7.1HIGH

Key Information:

Vendor: Element-hq
Status: Synapse
Vendor: CVE Published:; 27 March 2025

What is CVE-2025-30355?

CVE-2025-30355 refers to a significant vulnerability within the Synapse Matrix homeserver, an open-source implementation that facilitates decentralized communication across servers. This vulnerability allows a malicious actor to manipulate events sent to the Synapse homeserver, which can disrupt its ability to federate with other servers. Organizations relying on Synapse for communication may face severe operational disruptions, resulting in loss of connectivity and potential isolation within the Matrix ecosystem.

Technical Details

This vulnerability is characterized as an event manipulation flaw in Synapse versions up to 1.127.0. A malicious server can craft and send specific events that interfere with the federating process of the Synapse server. Once triggered, this manipulation prevents Synapse from properly communicating and exchanging data with other homeservers, which is a core function of the Matrix protocol. The issue has been acknowledged and resolved with the release of Synapse v1.127.1.

Potential Impact of CVE-2025-30355

Communication Disruption: Organizations may experience significant interruptions in their internal and external communication as the manipulated events prevent the homeserver from federating, leading to operational challenges.
Isolation Risks: Affected organizations could become isolated from other Matrix servers, limiting their ability to send or receive messages from connected federated servers. This may hamper critical operations and collaborations.
Reputation Damage: Persistent communication failures due to this vulnerability can negatively affect an organization’s reputation, as stakeholders may question the reliability and security of the communication platform being used.

Human OS v1.0:
Ageing Is an Unpatched Zero-Day Vulnerability.

Remediate biological technical debt. Prime Ageing uses 95% high-purity SIRT6 activation to maintain genomic integrity and bolster systemic resilience.

Deploy the Patch