What is CVE-2021-29433?

CVE-2021-29433 is a medium-severity vulnerability in Matrix Sydent, classified under Improper Input Validation. CVSS score: 4.3/10. Published 2021-04-15.

How severe is CVE-2021-29433?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Resource exhaustion in Matrix Sydent

CVE-2021-29433

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-04-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.009 (59.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 59.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Matrix Sydent
Matrix-Org Sydent — versions <= 2.2.0

Weakness classification (CWE)

References

github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553 (Patch, Third Party Advisory)
github.com/matrix-org/sydent/commit/3175fd358ebc2c310eab7a3dbf296ce2bd54c1da (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-29433?: CVE-2021-29433 is a medium-severity vulnerability in Matrix Sydent, classified under Improper Input Validation. CVSS score: 4.3/10. Published 2021-04-15.
How severe is CVE-2021-29433?: Medium severity. CVSS v3 base score is 4.3 out of 10.