Today we are disclosing CVE-2020-26890 / GHSA-4mp3-385r-v63f, a denial of service vulnerability affecting Synapse versions prior to 1.20.0. We strongly encourage all Synapse admins to upgrade as soon as possible. If you have not upgraded in a while, please refer to the upgrade notes, especially the latter portion of that document which covers any backwards incompatible changes which you may need to take into consideration.

As a best practice, we encourage Synapse admins to upgrade regularly, and either subscribe on GitHub or join #homeowners:matrix.org for low-traffic notifications of new releases.

We extend our thanks to Denis Kasak for reporting this issue, earning a second entry in the Matrix Security Hall of Fame.

The Foundation needs you

The Matrix.org Foundation is a non-profit and only relies on donations to operate. Its core mission is to maintain the Matrix Specification, but it does much more than that.

It maintains the matrix.org homeserver and hosts several bridges for free. It fights for our collective rights to digital privacy and dignity.

Support us