Matrix Sydent

Sydent does not verify email server certificates

SSRF in Sydent due to missing validation of hostnames

Denial of service attack via memory exhaustion

An issue was discovered in Matrix Sydent before 1.0.3 and Synapse before 0.99.3.1. Random number generation is mishandled, which makes it easier for attackers to predict a Sydent authentication token or a Synapse random ID.

util/emailutils.py in Matrix Sydent before 1.0.2 mishandles registration restrictions that are based on e-mail domain, if the allowed_local_3pids option is enabled. This occurs because of potentially unwanted behavior in Python, in which an email.utils.parseaddr call on user@bad.example.net@good.example.com returns the user@bad.example.net substring.

Malicious users could control the content of invitation emails

Denial of service (via resource exhaustion) due to improper input validation