CVE-2021-29433: Matrix Sydent

Medium severity, CVSS 4.3. EPSS: 0.9% chance of exploitation in the next 30 days.

Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.

Affected products

• Matrix Sydent: before 2.3.0 (fixed in 2.3.0)

Published 2021-04-15. Last modified 2026-06-17.