CVE-2021-21333 HTML injection in email and account expiry notifications

2021-03-2620:00:19

CWE-74

GitHub_M

www.cve.org

html injection

email notifications

account expiry

synapse

matrix

python

cve-2021-21333

security vulnerability

CVSS3

6.1

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality Impact

NONE

Integrity Impact

HIGH

Availability Impact

NONE

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

AI Score

Confidence

High

EPSS

0.001

Percentile

44.0%

JSON

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.

CNA Affected

[
  {
    "product": "synapse",
    "vendor": "matrix-org",
    "versions": [
      {
        "status": "affected",
        "version": "< 1.27.0"
      }
    ]
  }
]