MEDIUM6.1
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 2.0MEDIUM 4.3
CVSS:2.0/AV:N/AC:M/Au:N/C:N/I:P/A:NCVSS 3.xMEDIUM 6.1
CVSS:3.x/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NReferences
- https://github.com/matrix-org/synapse/pull/8444
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory
- https://github.com/matrix-org/synapse/pull/8444
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory