| CVE-2020-26891 | Date: (C)2020-10-20 (M)2023-12-22 |
AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.
CVSS Score and Metrics +CVSS Score and Metrics -| CVSS V3 Severity: | CVSS V2 Severity: |
| CVSS Score : 6.1 | CVSS Score : 4.3 |
| Exploit Score: 2.8 | Exploit Score: 8.6 |
| Impact Score: 2.7 | 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: NONE | Authentication: NONE |
| User Interaction: REQUIRED | Confidentiality: NONE |
| Scope: CHANGED | Integrity: PARTIAL |
| Confidentiality: LOW | Availability: NONE |
| Integrity: LOW | |
| Availability: NONE | |
| | |
