===========================
Due to the two security issues highlighted below, server administrators are
encouraged to update Synapse. We are not aware of these vulnerabilities being
exploited in the wild.
Security advisory
-----------------
The following issues are fixed in v1.23.1 and v1.24.0.
- There is a denial of service attack
([CVE-2020-26257](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26257))
against the federation APIs in which future events will not be correctly sent
to other servers over federation. This affects all servers that participate in
open federation. (Fixed in [#8776](https://github.com/matrix-org/synapse/pull/8776)).
- Synapse may be affected by OpenSSL
[CVE-2020-1971](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-1971).
Synapse administrators should ensure that they have the latest versions of
the cryptography Python package installed.
To upgrade Synapse along with the cryptography package:
* Administrators using the [`matrix.org` Docker
image](https://hub.docker.com/r/matrixdotorg/synapse/) or the [Debian/Ubuntu
packages from
`matrix.org`](https://github.com/matrix-org/synapse/blob/master/INSTALL.md#matrixorg-packages)
should ensure that they have version 1.24.0 or 1.23.1 installed: these images include
the updated packages.
* Administrators who have [installed Synapse from
source](https://github.com/matrix-org/synapse/blob/master/INSTALL.md#installing-from-source)
should upgrade the cryptography package within their virtualenv by running:
```sh
<path_to_virtualenv>/bin/pip install 'cryptography>=3.3'
```
* Administrators who have installed Synapse from distribution packages should
consult the information from their distributions.
Internal Changes
----------------
- Add a maximum version for pysaml2 on Python 3.5. ([\#8898](https://github.com/matrix-org/synapse/issues/8898))