| CVE-2021-21393 | Date: (C)2021-04-15 (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 1.28.0 Synapse is missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. Note that the groups feature is not part of the Matrix specification and the chosen maximum lengths are arbitrary. Not all clients might abide by them. Refer to referenced GitHub security advisory for additional details including workarounds.
CVSS Score and Metrics +CVSS Score and Metrics -| CVSS V3 Severity: | CVSS V2 Severity: |
| CVSS Score : 6.5 | CVSS Score : 4.3 |
| Exploit Score: 2.8 | Exploit Score: 8.6 |
| Impact Score: 3.6 | Impact Score: 2.9 |
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| CVSS V3 Metrics: | CVSS V2 Metrics: |
| Attack Vector: NETWORK | Access Vector: NETWORK |
| Attack Complexity: LOW | Access Complexity: MEDIUM |
| Privileges Required: LOW | Authentication: NONE |
| User Interaction: NONE | Confidentiality: NONE |
| Scope: UNCHANGED | Integrity: NONE |
| Confidentiality: NONE | Availability: PARTIAL |
| Integrity: NONE | |
| Availability: HIGH | |
| | |
