GHSA-4mp3-385r-v63f

Denial of service attack due to invalid JSON

Source: GitHub Advisory Database (reviewed) High CVE-2020-26890

Packages

Ecosystem	Package	Affected	Fixed in
PyPI	matrix-synapse	< 1.20.0	1.20.0

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact A denial of service attack against Matrix clients can be exploited by sending an event including invalid JSON data to Synapse. Synapse would relay the data to clients which could crash or hang. Impact is long-lasting if the event is made part of the room state. ### Patches At a minimum #8106 and #8291 must be applied. #7372 and #8124 include additional checks. ### Workarounds There are no known workarounds. ### Upgrading notes If an invalid event is accepted by an earlier Synapse it can become part of the room state and will not be fixed by upgrading Synapse. Redacting the invalid event should avoid clients receiving the invalid event.

References

External links from the advisory. They lead to third-party sites.