CVE-2021-29433

Name: CVE-2021-29433
Creator: NVD / NIST
Published: 2021-04-15T18:15:12.497+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.93%

Last modified Jun 17, 2026

CVE-2021-29433 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.93% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS Probability

0.93%

55.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Matrix	Sydent	< 2.3.0

References

https://github.com/matrix-org/sydent/commit/3175fd358ebc2c310eab7a3dbf296ce2bd54c1daPatch, Third Party Advisory
https://github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553Patch, Third Party Advisory
https://github.com/matrix-org/sydent/commit/3175fd358ebc2c310eab7a3dbf296ce2bd54c1daPatch, Third Party Advisory
https://github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553Patch, Third Party Advisory

Timeline

Published: Apr 15, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29433?

How severe is CVE-2021-29433?

CVE-2021-29433 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.93% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29433?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-29433?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST