CVE Vulnerabilities

CVE-2021-21333

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Published: Mar 26, 2021 | Modified: Nov 21, 2024
CVSS 3.x
6.1
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N
CVSS 2.x
2.6 LOW
AV:N/AC:H/Au:N/C:N/I:P/A:N
RedHat/V2
RedHat/V3
Ubuntu
LOW

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.27.0, the notification emails sent for notifications for missed messages or for an expiring account are subject to HTML injection. In the case of the notification for missed messages, this could allow an attacker to insert forged content into the email. The account expiry feature is not enabled by default and the HTML injection is not controllable by an attacker. This is fixed in version 1.27.0.

Weakness

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

Affected Software

Name Vendor Start Version End Version
Synapse Matrix * 1.27.0 (excluding)
Matrix-synapse Ubuntu bionic *
Matrix-synapse Ubuntu groovy *
Matrix-synapse Ubuntu trusty *
Matrix-synapse Ubuntu upstream *

Potential Mitigations

References