CVE-2021-21333: Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse)

Description

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.

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N

Attack vector

Network

Complexity

High

Privileges

None

User interaction

Required

Confidentiality

None

Integrity

High

Availability

None

Scope

Changed

Exploitation

Is it being used?

Exploit prediction (EPSS)1.4% · higher than 71% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

FE

Fedora · Fedoraproject

34 · source: NVD

SY

Synapse · Matrix

before 1.27.0 · source: NVD