Denial of Service Vulnerability in Matrix Synapse by Matrix

CVE-2020-26890

What is CVE-2020-26890?

Matrix Synapse, prior to version 1.20.0, inaccurately allows the inclusion of non-standard JSON values such as NaN, Infinity, and -Infinity in m.room.member event fields. This flaw poses a significant risk, as it can be exploited by remote attackers to execute denial of service attacks, affecting the federation and common Matrix clients. If a maliciously crafted event is accepted into the room state, its consequences are enduring, necessitating manual redaction to mitigate the issue, rather than a simple upgrade. Furthermore, the replication of these events across servers means that the impact is not limited to the original sender’s server.

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