Arch Linux Security Advisory ASA-202011-23

Severity: High
Date    : 2020-11-26
CVE-ID  : CVE-2020-26890
Package : matrix-synapse
Type    : denial of service
Remote  : Yes
Link    :


The package matrix-synapse before version 1.20.1-1 is vulnerable to
denial of service.


Upgrade to 1.20.1-1.

# pacman -Syu "matrix-synapse>=1.20.1-1"

The problem has been fixed upstream in version 1.20.1.




Matrix Synapse before 1.20.0 erroneously permits non-standard NaN,
Infinity, and -Infinity JSON values in fields of events,
allowing remote attackers to execute a denial of service attack against
the federation and common Matrix clients. If such a malformed event is
accepted into the room's state, the impact is long-lasting and is not
fixed by an upgrade to a newer version, requiring the event to be
manually redacted instead. Since events are replicated to servers of
other room members, the impact is not constrained to the server of the
event sender.


A remote attacker might be able to cause a denial of service via a
crafted event.