| CVE-2021-21333 | Date: (C)2021-03-29 (M)2023-12-22 |
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 Score and Metrics +CVSS Score and Metrics -| CVSS V3 Severity: | CVSS V2 Severity: |
| CVSS Score : 6.1 | CVSS Score : 2.6 |
| Exploit Score: 1.6 | Exploit Score: 4.9 |
| Impact Score: 4.0 | Impact Score: 2.9 |
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| CVSS V3 Metrics: | CVSS V2 Metrics: |
| Attack Vector: NETWORK | Access Vector: NETWORK |
| Attack Complexity: HIGH | Access Complexity: HIGH |
| Privileges Required: NONE | Authentication: NONE |
| User Interaction: REQUIRED | Confidentiality: NONE |
| Scope: CHANGED | Integrity: PARTIAL |
| Confidentiality: NONE | Availability: NONE |
| Integrity: HIGH | |
| Availability: NONE | |
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