---
id: CVE-2021-29432
aliases:
  - GHSA-mh74-4m5g-fcjx
  - PYSEC-2021-23
title: Malicious users could abuse Sydent to control the content of invitation emails
summary: Malicious users could abuse Sydent to control the content of invitation emails
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
vendor: matrix-sydent
product: matrix-sydent
ecosystem: pip
affected:
  - matrix-sydent < 2.3.0
patched:
  - matrix-sydent 2.3.0
published: '2021-04-19'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:49:03.750948873Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-mh74-4m5g-fcjx'
references:
  - url: >-
      https://github.com/matrix-org/sydent/security/advisories/GHSA-mh74-4m5g-fcjx
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-29432'
  - url: >-
      https://github.com/matrix-org/sydent/commit/4469d1d42b2b1612b70638224c07e19623039c42
  - url: 'https://github.com/matrix-org/sydent/releases/tag/v2.3.0'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/matrix-sydent/PYSEC-2021-23.yaml
  - url: 'https://pypi.org/project/matrix-sydent'
tags:
  - osv
  - pip
epss: 0.00934
epssPercentile: 0.59049
ingestedAt: '2026-09-12T03:13:01.711Z'
---

## Overview

### Impact

A malicious user could abuse Sydent to send out arbitrary emails from the Sydent email address. This could be used to construct plausible phishing emails, for example.

### Patches

Fixed in 4469d1d, 6b405a8, 65a6e91.

Note that these patches include changes to the *default* email templates. If these templates have been locally modified, they must also be updated.

### For more information

If you have any questions or comments about this advisory, email us at security@matrix.org.

## Affected packages

- `matrix-sydent < 2.3.0`

## Remediation

Upgrade to a patched release:

- `matrix-sydent 2.3.0`